Pleated filtration media having tapered flutes

ABSTRACT

Pleated filtration media, media packs, filter elements, and methods for filtering fluid are provided which contain three dimensional tapered flutes in the media surface, the flutes configured to improve filter performance. In certain embodiments the flutes have defined peaks that reduce masking between adjacent pleats, the flutes have ridges along their length to modify flute cross sectional geometry, and/or the flutes provide for volume asymmetry across the media.

PRIORITY

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/298,109, entitled “PLEATED FILTRATION MEDIAHAVING TAPERED FLUTES,” filed Jan. 25, 2010, the contents of which isherein incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to pleated filtration media, media packs,filter elements, and methods of making media, media packs, and filterelements.

BACKGROUND

Fluid streams, such as gases and liquids, often carry contaminantmaterial therein. In many instances, it is desirable to filter some orall of the contaminant material from the fluid stream. For example,particulate contaminants are often present in air streams to engines formotorized vehicles and for power generation equipment, air and gasstreams to gas turbine systems, air and gas streams to variouscombustion furnaces, and air and gas streams to heat exchangers (e.g.,heating and air conditioning). Liquid streams in engine lube systems,hydraulic systems, coolant systems and fuel systems, can also carrycontaminants that should be filtered. It is preferred for such systemsthat selected contaminant material be removed from the fluid (or haveits level reduced in the fluid). A variety of fluid filters (gas orliquid filters) have been developed for contaminant reduction. Ingeneral, however, continued improvements are sought.

Pleated filtration media has been in use for many years, and is widelyadopted for fluid filtration applications, including gas and liquidfiltration. Pleated filtration media provides a relatively large mediasurface area in a given volume by folding the media back and forth suchthat a large amount of media can be arranged in a relatively smallvolume. Pleated media is typically formed from continuous or rolled websof filter media, with the pleats formed perpendicular to the machinedirection of the media. The machine direction of the media generallyrefers to the continuous direction of the media as it comes from asource, such as a supply roll. The continuous direction is alsosometimes referred to as the machine direction of the media. The pleatfolds, therefore, are generally transverse to the continuous directionof the media. In general, a first set of pleat folds forms a first faceof the media pack and a second set of pleat folds forms a second face ofthe media pack, with the first and second pleat folds alternating withone another. It will be understood that in certain embodiments the“face” described herein can be substantially uneven or irregular, andcan be planer or non-planer.

One challenge to designing filter elements containing pleated filtermedia is that an undesirable level of fluid flow restriction can occuras the number of pleats within a given volume increases. Thisrestriction becomes critical as the pleats are pressed too close to eachother, which can cause significant interference with filter performance.For example, pleats can be so close together that it is difficult for afluid to enter the area between the pleats. Due to this restriction, themedia in some prior pleated filters is modified to create an unevensurface with raised areas of shallow repeating arcs along the mediasurface. As pleats having this uneven surface become pressed toward oneanother, the raised areas on the media help maintain fluid flow betweenpleat surfaces by forming channels which aid fluid flow. Although pleatswith uneven surfaces can provide advantages, the improvement is limited,especially with deeper pleat constructions.

Therefore, a need exists for improved pleated filtration media.

SUMMARY

The present invention is directed to pleated filtration media andfiltration media pleat packs containing the pleated filtration media.These pleat packs can in turn be formed into filter elements, which arealso the subject of the present invention. The media and media pleatpacks contain flutes extending between the pleat folds. The flutes arethree dimensional structures formed in the filtration media that provideadvantageous flow paths along the surfaces of the pleats, that allow foradvantageous flow of fluids through the media, that assist incontrolling pleat spacing, that aid in providing rigidity and structureto the pleat face, and that provide for efficient contaminant removal.

At least some of the flutes in the media pack have a tapered geometry.The tapered geometry typically includes a change in the width, and/orheight, and/or cross sectional areas of flutes along their length. Theuse of tapered flutes in a pleated media can have significant benefitsin regard to filtering performance. For example, tapered flutes canallow for deeper pleat packs to be formed while offering benefits influid flow through the pleat pack. Such benefits can be realized byhaving flutes with relatively large cross sectional areas on theupstream side of the media pack near the front face of the media pack(where fluids enter the media pack), along with opposing flutes havingrelatively large cross sectional areas on the downstream side of themedia pack near the back face of the media pack (where fluids exit themedia pack). This changing of upstream and downstream flute crosssectional areas can decrease contraction and expansion pressure lossesassociated with flow entering and exiting the pleat pack, and can reducepressure losses as flow moves along channels formed by tapered flutes.Thus, tapered flutes then can reduce pleat pack initial pressure drop.By reducing initial pressure drop, and affecting the flow distributionthrough media along flutes, tapered flutes can increase filter capacityand life.

The changes in width, height and/or cross sectional area are oftengradual along the length of the flutes, but in some implementations thechanges can be step-wise or otherwise non-gradual. In mostimplementations the tapered flutes will display a substantially uniformtaper along all or most of the flute length. However, in someimplementations it is possible to have the taper vary along the flutelength, so that the taper is not uniform or not continuous. For example,the flute may transition from a tapered area to a non-tapered area, toanother tapered area.

Although the cross-sectional area of specific flutes may vary from oneend of the flute to the other, it is not necessary that the width of theflute or the height of the flute also taper. Indeed, in someimplementations the width, the height, or both are constant orsubstantially constant along the length of the flute. As will beexplained in the Detailed Description, it is possible to change thecross sectional area of a flute without changing its width or height.This can be done by changing the shape of the side walls of the flute,such as by forming ridges along the flute wall and modifying theposition of those ridges along the flute. As used herein, a ridge isgenerally a defined bend, crease, or deformation in the media along someor all of the length of a flute. A ridge is typically a discontinuity inthe curve of the media, which is not found in generally curving media.Thus, a ridge is generally not simply an inflection point between orgradual curve, but rather a more significant discontinuity in thecurvature (as shown, for example, in FIGS. 9A and 9B of the presentinvention). As is elaborated in the Detailed Description, ridgesconstructed in accordance with the teachings of the invention allow forspecialized tapered flutes. In particular, it possible to have theposition of ridges varies along the length of the flutes so as topromote controlled taper of the flutes. Thus, the addition of formedridges along the length of a flute, and the changing of those ridgeshapes and locations, can result in significant tapering of the flutecross sectional area; and such tapering can optionally be conductedwithout significant changes to height or width of the flute.

The pleated media of the present invention is further advantageous inthat the tapered flutes allow for high utilization levels of the filtermedia. By high utilization levels it is meant that there is relativelylittle masking of the media. As used herein, masking refers to the areaof proximity between adjacent and touching media faces. Where upstreamor downstream adjacent media faces touch, there is a lack of substantialpressure difference across the media or there is significant resistanceto flow across the media that is greater than would be observed if thesheets were not in close proximity. In general, masking is experiencedat the location in the media where there is close proximity or contactto another media sheet or flow bounding surface. This close proximitycan result in a decrease in pressure to drive flow through the media atthat location. As a result, masked media is not as useful to thefiltration performance of filtration media. Significant reduction inmasking of media can represent a major improvement in filter performanceand design because it increase the amount of media available forfiltering the fluid.

Accordingly, it is desirable to reduce masking so as to increase theamount of filtration media available for filtration. Reduction inmasking increases the dust storage capacity of the filtration mediapleat pack, increases the throughput of fluids through the filtrationmedia for a given pressure drop, and/or decreases the pressure drop ofthe filtration media pleat pack for a given overall fluid flow rate.Flutes in the pleated media made in accordance with the teachings of thepresent invention allow for a reduction in masking of the media. Thisreduction is accomplished by controlling the shape of the flutes, inparticular by having flute tips that have reduced surface area incontact with flutes on adjacent pleats. Sharp flute tips can be createdby having a sharp radius or a defined tip that reduces masking betweenpleats. As will be described in the Detailed Description, in variousembodiments of the invention the sharp flute tips are simultaneouslyformed in conjunction with ridges along the flute, so as to increase themedia surface area, to create tapered flutes, and to otherwise controlfilter media performance.

While the specific media area subject to masking along a given flute maybe relatively small, the total amount of masked media over an entirefilter element can be substantial. Therefore even modest improvements atreducing masking can have significant value. It is possible to reducethe amount of masked media in a filter element while simultaneouslymodifying flute geometry to even further increase the amount ofeffective media present in the filter. By reducing masking, theperformance or life of the filter element can be increased, or the sizeof the filter element can be reduced while maintaining the sameperformance or filter life. In general, enhancing the filter elementlife or decreasing filter initial pressure drop for a given filterelement size or reducing the filter element size for a given filterelement performance can be referred to as enhancing the filter'sperformance. The tapered flutes of the present invention can beconstructed with reduced masking of the media, even though the width,height, or cross section of the flutes are varied along their length;and this ability to limit masking allows for increased filterperformance as a result of maximizing useful media.

Pleated media made in accordance with the invention is furtheradvantageous in that the tapered flutes can be constructed such thatthere is little strain on the media during production, allowingrelatively non-stretchable media to be formed into tapered flutesrunning directionally from one pleat face to the other pleat face of apleated media pack. Media having high cellulose content is oftendesirable due to its low cost, and the present invention allows forincorporation of high-cellulose media and formation of suitable taperedflutes without unacceptable damage of the media. Similarly, media havinghigh glass fiber content can be used and formed into tapered fluteswithout unacceptable degradation of the media.

In certain embodiments the filtration media pleat packs made inaccordance with the invention are constructed with flutes that havedifferent flute shapes such that there are different open volumes on theupstream and downstream sides of the pleat pack, a property referred toherein as pleat pack volumetric asymmetry. This pleat pack volumetricasymmetry can, in some embodiments, promote contaminant materialstorage, improved flow and better filtration. Pleat pack volumetricasymmetry can be particularly helpful for improving performance infilter configurations that have shallow pleat packs. Pleat packvolumetric asymmetry is distinct from tapering of flutes, but incombination the volumetric asymmetry and tapering can result insignificant improvements in pleat pack performance and useful life.Indeed, tapering of flutes can be used to create or increase volumetricasymmetry.

The present invention is also directed to pleated filtration mediapacks. The phrase “pleated filtration media pack” refers to a media packconstructed or formed by folding, pleating, or otherwise formingfiltration media into a three-dimensional network. A pleated filtrationmedia pack can be referred to, more simply, as a media pack. Pleatedfiltration media packs can optionally be combined with other featuresfound in filter elements including a seal, a seal support, and pleatpack end encapsulation. In general, a pleated filtration media packincludes filtration media having a first set of pleat folds forming afirst face, a second set of pleat folds forming a second face, and thefiltration media extending between the first set of pleat folds and thesecond set of pleat folds in a back and forth arrangement.

The folds are typically formed transverse to the machine direction ofthe media, but that is not a requirement. The folds can be formed at anangle that is different than an angle transverse to the machinedirection. The first face is generally the inlet or outlet of thepleated filtration media, and the second face is the other of the inletor outlet of the filtration media. For example, unfiltered fluid canenter the pleated filtration media pack via the first face, and filteredfluid can exit the pleated filtration media pack via the second face, orvice versa.

Pleated media made in accordance with the invention can be assembledinto numerous shapes and configurations, including panel filters,cylindrical filters, and conical filters. In panel filters, pleatedmedia typically extends in a planar or panel configuration having afirst face of the pleated media formed from a first set of pleat folds(also called pleat tips) and a second face of the pleated media formedfrom a second set of pleat folds (also called pleat tips). The first andsecond faces formed by the pleat folds are generally parallel. Fluidflows into the panel filter through one face and out of the panel filterthrough the other face.

In cylindrical or conical filters, pleated media is generally formedinto a tube or cone (or a partial section of a tube or cone), with afirst face of the pleated media (formed by a first set of pleat folds)creating an interior face, and the second face of the pleated media(formed by a second set of pleat folds) forming an outside face. In thecase of cylindrical and conical filters for air filtration, airtypically flows into the filter element from the outside face to theinterior face (or vice versa in what are sometimes referred to asreverse flow filters).

The above summary of the present invention is not intended to describeeach disclosed embodiment of the present invention. This is the purposeof the detailed description and claims that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a filter element according to theprinciples of the invention.

FIG. 2A is a front view of the filter element of FIG. 1.

FIG. 2B is a close-up front view of the filter element of FIG. 1.

FIG. 3A is a back view of the filter element of FIG. 1.

FIG. 3B is a close-up back view of the filter element of FIG. 1.

FIG. 4 is a side view of the filter element of FIG. 1, showing a seriesof planes dividing the filter element into cross sections depicted inFIG. 5A-5C

FIG. 5A is a close-up cross section of filtration media from the filterelement of FIG. 1, the cross section taken along plane A-A′ of FIG. 5.

FIG. 5B is a close-up cross section of filtration media from the filterelement of FIG. 1, the cross section taken along plane B-B′ of FIG. 5.

FIG. 5C is a close-up cross section of filtration media from the filterelement of FIG. 1, the cross section taken along plane C-C′ of FIG. 5.

FIG. 6 is a close-up perspective view of a portion of a sheet offiltration media taken from filter element of FIG. 1.

FIG. 7 is a close-up perspective view of an individual flute taken fromthe filter element of FIG. 1.

FIG. 8A is a cross sectional view of a portion of a sheet of filtrationmedia shown in FIG. 7, the cross section taken along lines A-A′ of FIG.7.

FIG. 8B is a cross sectional view of a portion of a sheet of filtrationmedia shown in FIG. 7, the cross section taken along lines B-B′ of FIG.7.

FIG. 8C is a cross sectional view of a portion of a sheet of filtrationmedia shown in FIG. 7, the cross section taken along lines C-C′ of FIG.7.

FIG. 8D is a cross sectional view of a portion of a sheet of filtrationmedia shown in FIG. 7, the cross section taken along lines D-D′ of FIG.7.

FIGS. 9A-9C are enlarged, schematic, cross-sectional views of filtrationmedia according to the principles of the invention.

FIG. 10 is an enlarged cross sectional view of fluted media constructedin accordance with an implementation of the invention.

FIG. 11A is an enlarged, schematic cross-sectional view of a portion ofa filtration media pack according to principles of the invention.

FIG. 11B is an enlarged, schematic cross-sectional view of a portion ofa filtration media pack according to principles of the invention.

FIG. 12 is a perspective end view of a portion of a pleated filtrationmedia pack according to the principles of the invention.

FIG. 13 is an enlarged partial perspective view of a portion of afiltration media pack made in accordance with an implementation of theinvention.

FIG. 14 is an enlarged partial perspective view of a sheet of flutedfiltration media made in accordance with an implementation of theinvention.

FIG. 15 is a partial top plan view of a continuous sheet of formedfilter media with embossed flutes.

FIG. 16 is a partial top plan view of a continuous sheet of formedfilter media with embossed flutes.

FIG. 17 is an enlarged scanned cross-sectional image of a fluteaccording to principles of the invention, showing a method to measurethe effective inner radius of a flute.

FIG. 18 is a schematic diagram of an apparatus for forming fluted mediain accordance with an implementation of the invention.

FIG. 19A is a top schematic diagram of the sheet of filter media beingtransformed from a flat continuous sheet to a fluted and pleated media.

FIG. 19B is a side schematic diagram of sheet of filter media from FIG.19A being transformed from a flat continuous sheet to a fluted andpleated media.

FIG. 20 is a side perspective view of a bunching mechanism made inaccordance with an implementation of the invention, the bunchingmechanism configured to gather media in the cross-web direction forsubsequent formation into flutes.

FIG. 21 is a side perspective view of a bunching mechanism and formingrollers made in accordance with an implementation of the invention, thebunching mechanism configured to gather media in the cross-web directionfor subsequent formation into flutes.

FIG. 22 is a side perspective view of forming rollers made in accordancewith an implementation of the invention, the forming rollers configuredto create flutes in filter media.

FIG. 23 is a side perspective view of alternative forming rollers madein accordance with an implementation of the invention, the formingrollers configured to create flutes in filter media.

FIG. 24 is an exploded perspective view of a forming roller made inaccordance with an implementation of the invention, the forming rollerconfigured to create flutes in filter media.

FIG. 25 is a cross section of a forming roller made in accordance withan implementation of the invention, the forming roller configured tocreate flutes in filter media.

FIG. 26 a perspective view of a segment of a forming roller depicted inFIG. 25.

FIG. 27A to 27C are cross sectional schematics demonstrating variousspacing of the score-bars on a segmented nip roller, the score barsconfigured for forming proper pleat folds in continuous media.

FIG. 28 is a schematic diagram of an apparatus for forming fluted mediain accordance with an implementation of the invention.

FIG. 29 is a schematic diagram of an apparatus for forming fluted mediain accordance with an implementation of the invention.

FIG. 30 is a perspective view of a portion of a cylindrical filtrationmedia pack according to the principles of the invention.

FIG. 31 is a perspective view of a portion of the cylindrical filtrationmedia pack of FIG. 30 and showing outside to inside flow of fluidthrough the filtration media pack.

FIG. 32 is a side elevation view of a cylindrical filter element with aportion broken away.

FIG. 33 is a perspective view of the cylindrical filter element of FIG.32.

FIG. 34 is a schematic side elevation view of one type of a conicalfilter element.

These drawings are to be considered general representations of theinvention, and it will be appreciated that they are not drawn toencompass all embodiments of the invention, nor are they always drawn toscale. It will also be understood that media made in accordance with theinvention will generally exhibit variation.

While the invention is susceptible to various modifications andalternative forms, specifics thereof have been shown by way of exampleand drawings, and will be described in detail. It should be understood,however, that the invention is not limited to the particular embodimentsdescribed. On the contrary, the intention is to cover modifications,equivalents, and alternatives falling within the spirit and scope of theinvention.

DETAILED DESCRIPTION

The present invention is directed to pleated filtration media andfiltration media pleat packs that contain flutes extending directionallybetween the pleat folds, as well as methods and equipment for producingpleated filtration media and media pleat packs. The flutes are threedimensional structures formed in the filtration media that provideadvantageous flow paths along the pleat surfaces, allow for advantageousflow of fluids through the media, and provide for efficient contaminantremoval.

At least some of the flutes in the media and pleat packs have a taperedgeometry. The tapering is typically manifest by a change in the width,height, and/or cross sectional area of a flute along at least a portionof its length. Although the cross-sectional area of specific flutes mayvary from one end of a flute to the other, it is not necessary that thewidth of the flute or the height of the flute also taper. Indeed, insome implementations the width, the height, or both are constant orsubstantially constant along the length of the flute, while the crosssectional area of the flute changes. In other implementations the heightand width of the flutes changes along their length.

The changes in width, height and/or cross sectional area are oftengradual along the length of the flutes, but in some implementations thechanges can be step-wise or otherwise non-gradual. In manyimplementations the tapered flutes display a substantially uniform taperalong all or most of the flute length. However, in some implementationsit is possible to have the taper vary along the flute length, so thatthe taper is not uniform. In some implementations it is possible thatonly portions of one or more flutes exhibit taper, while other portionsof one or more flutes are substantially straight. Generally the taperedflutes do not get wider and then narrower along their length. In otherwords, typically a flute that is tapering down in cross sectional areawill not switch to tapering up in cross sectional area; and a flute thatis tapering up in cross sectional area will not taper down in crosssectional area. However, in some implementations discontinuous taperingcan occur, such as a flute that tapers down in cross sectional area forpart its length, followed by tapering up in cross sectional area,followed by tapering down again in cross sectional area. In some suchimplementations the starting and ending cross sectional areas of theflute do not change, but tapering of the cross sectional area occursalong portions of the flute.

The use of tapered flutes in pleated media can have significant benefitsin regard to filtering performance. For example, tapered flutes canallow for use of deeper pleat packs while offering benefits in fluidflow through the media. Such benefits can be realized by having fluteswith relatively large cross-sectional areas on the upstream side of themedia pack near the front face (where fluids enter the media pack),along with opposing flutes on the downstream side of the media pack nearthe back face (where fluids exit the media pack) which also haverelatively large cross-sectional areas. This changing of upstream anddownstream flute cross sectional areas decreases pleat pack areacontraction entrance pressure losses associated with flow entering thepleat pack and pleat pack area expansion exit pressure losses associatedwith flow exiting the pleat pack. Flow uniformity may be used tobeneficially decrease media and/or channel pressure losses as flow movesalong flutes and through media formed by tapered flutes. More uniformflow through media in flutes can provide more uniform dust loadingwithin flutes. Tapered flutes then can be used to reduce pleat packinitial pressure drop. By reducing initial pressure drop, and affectingthe flow distribution through media along flutes, tapered flutes may beused to increase filter dust capacity (filter life). By reducingpressure losses and increasing flow uniformity, tapered flutes also areparticularly well suited to media that will be pulse cleaned by reversalof fluid flow through the filter element. Pleated media with taperedflutes may also be useful for various other filtering applications.

The pleated filtration media pack can be used to filter a fluid that canbe a gaseous or liquid substance. An exemplary gaseous substance thatcan be filtered using the filtration media is air, and exemplary liquidsubstances that can be filtered using the filtration media includewater, oil, fuel, and hydraulic fluid. The filtration media pack can beused to separate or remove at least a portion of a component from afluid to be filtered. The component can be a contaminant or anothermaterial targeted for removal or separation. Exemplary contaminants andmaterials targeted for removal include those characterized as solids,liquids, gases, or combinations thereof. The contaminants or materialstargeted for removal can include particulates, non-particulates, or amixture thereof. Materials targeted for removal can include chemicalspecies that can be captured by the media. The reference to removal ofcomponents and contaminants should be understood to refer to thecomplete removal or separation or a partial removal or separation.

Referring now to the figures, various example embodiments of theinvention will be described. FIGS. 1 through 6 show an example filterelement constructed in accordance with the invention. While exampleflutes on opposing pleat faces in this example filter element are shownsubstantially touching along the entire flute's length, it is understoodthat flutes of this invention may not touch along their length or maytouch only occasionally along their length. FIG. 1 shows a filterelement 100 from a front perspective view. The filter element 100includes a frame 102 surrounding pleated filter media 110. The frontface 108 of filter media 110 is shown in FIG. 1, and the filter media110 has a corresponding back face 109 shown in FIG. 3. In addition, theframe has a right side 104, a left side 105, a top 106, and a bottom107.

FIG. 2A shows a schematic front view of the filter element 100 depictedin FIG. 1, with FIG. 2B showing a simplified close-up view of the frontface of pleated filter media 110. The close-up view of the pleatedfilter media 110 depicts an end view of the pleats 120, including thetips 122 of numerous pleats, along with a space 124 between each pleat.It will be understood that the close-up view of the pleated mediaremains substantially schematic in presentation, and is thus notintended to be a detailed representation of actual media.

The front face 108 of the filter media 110 is typically the “upstream”side of filter element 100, and the back face 109 (shown in FIGS. 3A and3B) is the “downstream” side of the filter element 100. Thus, in atypical embodiment, the flow of fluids through the filter element 100 isfrom the front face 108, into the interior of filter element, and thenout through the back face 109 (while passing through the filter media110). The back face 109 shown in FIG. 3B depicts a simplified schematicview of the pleat pack surface, including a plurality of pleats 121 withpleat tips 123 and spaces 125 between the pleats 121.

Reference is now made to FIGS. 4, 5A, 5B, and 5C, which show furtherdetails of an example of pleated media having tapered flutes made inaccordance with the teachings of the invention.

FIG. 4 shows the right side panel 104 of the filter element 100 depictedin FIG. 1. Sections of planes A-A′, B-B′, and C-C′ are depicted in FIGS.5A to 5C. Plane A-A′ corresponds to a cross section of element 100 takennear the front face 108 of the element 100; plane B-B′ corresponds to across section of element 100 taken near the center of element 100,approximately half way between front face 108 and back face 109; planeC-C′ corresponds to a cross section of element 100 taken near the backface 109 of the element 100. Although sections A-A′ and B-B′ can betaken very close to adjacent front face 108 and back face 109, typicallythere will be at least modest deformation of the flutes at the locationwhere the pleat fold is made. Therefore, FIGS. 5A to 5C represent crosssections that are close to the pleat folds, but not necessarilyimmediately next to the pleat folds.

FIG. 5A shows a close-up of the media 110 taken along plane A-A′. Flutesthat are deemed to be upstream in the media pack are identified with thetitle “in” (because fluids are flowing into the pleat pack in theseflutes), while flutes that are designated downstream in the media packare identified with the title “out” (because fluids are flowing out ofthe pleat pack in these flutes). FIG. 5A shows upstream flutes 210surrounded by adjacent downstream flutes 220. A fluid entering a pleatpack by way of an upstream flute 210 is able to flow along the flute,but eventually passes through filter media 110 and then out of the pleatby way of a downstream flute 220 (with the exception of small amounts offluid that will pass through the actual pleat fold).

It will be observed in FIG. 5A that the upstream flutes 210 have asignificantly larger cross sectional area than the downstream flutes 220(at location A-A′ of FIG. 4). It will also be observed in FIG. 5A thatthere is relatively little masking between adjacent layers of filtermedia 110. As the flutes extend deeper into the filter element, theupstream flutes 210 begin to reduce, or taper down, in cross sectionalarea while the downstream flutes 220 begin to increase, or taper up, incross sectional area. By the center of the filter element, shown in FIG.5B, the downstream flutes 220 are substantially equal in cross sectionalarea to the upstream flutes 210. The tapering continues until the crosssection shown in FIG. 5C, where the upstream flutes 210 have asignificantly smaller cross sectional area than the downstream flutes220. Of note is the fact that this significant amount of tapering hasbeen accomplished in the depicted embodiment without any increase inmasking along the flute length, and while maintaining the height andwidth of the flutes and that the upstream and downstream flutes eachhave substantially the same perimeter length of media forming eachflute. In this example, only the cross sectional areas of each flutechange along the flute length. As will be further described later,alternative embodiments can change flute height and width. Thus, FIGS.5A through 5C show a useful embodiment of tapered flutes constructed inpleated media, but alternatives are possible while remaining within thescope of the invention.

It will also be observed, from FIGS. 5A to 5C that the tapered fluteconfiguration is accomplished with relatively little masking of mediabetween adjacent flutes, and with no change in the surface areaavailable for filtration. In other words, the tapering of the flutesoccurs without changes to the amount of exposed media on either theupstream or downstream flutes. The arrangement of the tapered flutes inFIGS. 5A to 5C show an implementation where the upstream side of themedia near the front face has large open flutes, and the downstream sideof the media near the back face also has large open flutes. The resultis a configuration allowing improved filter performance in manycircumstances, such as for relatively deep pleated filter elements,including those that are greater than 2 inches deep, greater than 6inches deep, and in particular greater than 10 inches deep.

FIG. 6 shows a section of a sheet of filter media 250 that will produceflute geometries consistent with the flutes shown in FIGS. 5A to 5C. Thesection of a sheet of media 250 reveals how the tapered flute transformsfrom relatively large upstream flutes 252 to relatively large downstreamflutes 254. In this view, which is drawn as a perspective view and notto scale, the numbers X₀ and X₁ are used to represent the width of thepleated media (or at least the section depicted, which is 4 fluteswide). Generally the pleated media is formed such that X₀ and X₁ areequal, which allows for media to be easily created that hasperpendicular sides. However, it should be understood that in someimplementations X₀ can be either greater or less than X₁. In suchconfigurations the difference in X₀ and X₁ can manifest itself by havingpleat packs wherein the dimensions of the front face of the pleat packare different than the dimensions of the back face of the pleat pack.While such variations will not be suitable for all applications, theability to alter pleat pack geometry is advantageous for someimplementations.

Of additional significance is that the tapered transitions evident inFIG. 6 from large to small flute cross sectional areas (and small tolarge flute cross sectional areas) can be created without significantstrain on the media sheet 250. In particular, the flutes can be createdwithout excess stretching of the media because the length of the mediaforming the flutes, when measured from side 256 to 258 is generallyequal along the pleat surfaces from a front face of the pleat pack to aback face of the pleat pack (e.g. the lengths are substantially the samemeasured at sections A-A′, B-B′, and C-C′ as represented in FIG. 4).Thus, tracing the distance along the front edge 257 of the media mayequal or nearly equal the distance traced along the back edge 259 incertain embodiments. Therefore, excess stretching of the media does nottypically occur in forming the flute geometries—a characteristic thatcan be very important to the production of fluted media usinghigh-cellulose filter media and glass fiber filter media, as well asother media that does not easily stretch without degradation. In exampleimplementations the amount of stretching of the media in the cross webdirection is less than 10 percent, often less than 7.5 percent, anddesirably less than 5 percent.

A further aspect of the fluted media made in accordance with animplementation of the invention is revealed by reference to FIG. 7,along with cross sections shown in FIGS. 8A, 8B, 8C, and 8D. Flute 252is shown tapering from a front face with a large upstream opening to aback face with a smaller upstream opening. The manner in which thistaper occurs is evident by reviewing cross sections taken along planeA-A′; plane B-B′; plane C-C′; and plane D-D′; corresponding respectivelyto FIGS. 8A, 8B, 8C, and 8D. In FIG. 8A the volume underneath the media255 is enhanced by having a ridge 270 that causes the media to extendoutwardly from the interior of flute 252. In addition, the flute 252includes peaks 260 that project upward slightly from the adjacent media(so as to reduce masking). Although this upward projection of peak 260is relatively subtle and can be difficult to visually observe, it stillaids in reduction of masking of the media.

Progressing down the flute 252, at cross section B-B′ shown in FIG. 8B,the peak 260 has become even more defined. In addition, the single ridge270 on each side of the peak 260 of FIG. 8A has diverged into two ridges270 on each side of peak 260. The two ridges help to modify the shape ofthe flute such that the cross sectional area of flute 252 is starting toshow a decrease from that shown in FIG. 8A. This change continuesthrough cross section C-C′ in FIG. 8C, where the peak 260 remains, butthe two ridges 270 on each side of the peak 260 have moved further fromthe peak 260, thereby even further diminishing the cross sectional areaof the flute 252. Finally, at the far end of flute 252, taken alongcross section D-D′, the cross sectional area of the flute is evensmaller, with peak 260 being very well defined, but with only one ridge270 evident, due to the second ridge merging into the edge 257 of theflute 252 (which also corresponds to a peak of an adjacent flute). Theflute geometry shown in FIGS. 7 and 8A-8D describe an example embodimentdemonstrating how the tapered flutes can be created, but are not meantto represent the exclusive manner in which such flutes can be formed.

Flute Features and Fluted Media Characteristics

Explanation will now be made of features of tapered flutes made inaccordance with the invention, including the presence of flute ridges,flute width and height, cord length of the flutes, media cordpercentages, media volume asymmetry, flute density, flute peak radius,and flute orientation.

Flute Ridges

Now referring to FIGS. 9A-9C, cross-sectional views of various flutedmedia sheets suitable for construction of tapered flutes are shown. Itwill be noted that FIGS. 9A-C are not intended to be scale drawings ofall acceptable flute geometries, but rather merely show exampleimplementations.

In FIG. 9A, a segment of fluted media sheet 300 is shown with flutes310. In addition, media sheet 300 also forms a flute 312 between flutes310. Although not depicted in FIG. 9A, media 310 would typically extendwith numerous additional flutes, and additional media sheets would bepresent in a media pack, such as shown in FIGS. 5A to 5C. The flutedmedia sheet 300 reveals a number of features which provide for superiorfiltration performance. One feature of the flutes 310 in media sheet 300is that the tallest extent at peaks 301 and 303 have a sharp tip orpoint, rather than simply a curved surface. A sharp tip or point may beapproximated by a model of the flute tip consisting of a relativelysmall radius. Sharp tips can be useful because large radii result inincreased masking of media when adjacent flutes from opposing pleatfaces touch. Flutes 310 further have peaks 302 and 304. The peaks 302,304 in media sheet 310 are more curved than the peaks 301 and 303.However, in other implementations the peaks 302 and 304 can beconstructed such that they are also relatively sharp. Flute peaks 301and 303 can be referred to as adjacent first side peaks, and the peaks302 and 304 can be referred to as adjacent second side peaks. Thecharacterization of certain peaks as first side peaks and other peaks assecond side peaks is arbitrary, and can be reversed, if desired.

The flutes 310 have a series of ridges 308 that help in defining theinterior volume and shape of the flutes 310. Ridges can be created inthe media as a result of deformation of the media at that location. Themedia can be deformed at the ridge as a result of applying pressure tothe media. Changing of the location of the ridges 308 can significantlyimpact the taper of flutes 310 while simultaneously changing the taperof opposed flutes 312. Thus, for example, movement of ridges 308 towardlower pleat peak 304 can result in increasing the cross sectional areaof flute 312 while decreasing the cross sectional area of flute 310. Insome such implementations the relative width to height ratio of theflutes can change, while in other implementations this ratio stayssubstantially constant.

The fluted media 300 is shown having two ridges 308 for each flute 310.The ridges 308 extend along at least a portion of the length of theflute. In some embodiments each ridge 308 can be characterized as ageneral area where a relatively flatter portion of the fluted media 308a joins a relatively steeper portion of the fluted media 308 b. The useof the term “ridge” is intended to characterize a portion of the mediathat is not considered a peak. That is, ridges can be provided betweenpeaks, and ridges can be considered non-peaks. A ridge can be considereda line of intersection between differently sloped media portions.

In some implementations the appearance of the ridge will be somewhatobscured by irregularities in the media itself. The characterization ofa ridge is not to be confused with the flute peaks. The characterizationof a generally flatter portion 308 a and a generally steeper portion 308b is intended as one way to characterize the presence of a ridge 308. Ingeneral, the flatter portion 308 a and the steeper portion 308 b mayexhibit some curve. That is, it is expected that the flatter portion 308a and the steeper portion 308 b will not be completely planar,particularly as fluids such as air or liquid flow through the mediaduring filtration. More specifically, a ridge can be a region oftransition between substantially differently sloped media portionswithin the profile of a section of fluted media. Ridges identifydiscontinuities in the curvature of the media, such as a crease or bend(see, e.g., 308 of FIG. 9A). The transition can be relatively abrupt.Under normal usage, ridges do not contact ridges from other adjacentpleats. Ridges promote efficiency of fluid flow and filtration throughthe media packs by allowing customization and optimization of the crosssectional area of the flutes, increases in the amount of media within aspecific volume, and aiding in reduction of masking between flutes onopposed media surfaces.

Proper ridges are particularly useful for tapering the cross sectionalarea of the flute without changing the height or width of the flute andwithout requiring significant stretching of the media. Also, ridges mayallow for tapered changes in the cross sectional area without changes inthe total surface area of the flute.

For the example fluted sheet 300, the relatively flatter portion of thefluted media 308 a can be seen in FIG. 9A as the portion of the flutedmedia extending between the peak 301 and the ridge 308. The relativelysteeper portion of the fluted media 308 b can be characterized as thatportion of the media extending from the peak 302 to the ridge 308. Thepresence of the ridges of the media shown in FIG. 9A helps provide forreduced masking at adjacent peaks 301 and 302. The presence of theridges 308 help increase the amount of media present between adjacentpeaks (e.g., peaks 301 and 302; or 301 and 304) and helps sharpen thepeaks.

It will also be observed that tapered flutes produced using ridgestypically also have tapered ridges, such as ridges that converge towardone another, diverge from one another, or converge upon a flute peak.Such convergence is apparent, for example, in FIGS. 7 and 8A to 8D,discussed above.

A ridge can be formed as a result of creasing, bending, folding, coiningor otherwise manipulating the media along a length of the fluted sheetduring the formation of the fluted media. It may be desirable, but it isnot always necessary, during the step of forming the fluted media totake steps to set the ridge. Setting the ridge means removing residualstress within the media in the ridge so that the media tends to stay inthe formed shape. For example, the ridge can be set by heat treatment ormoisture treatment or a combination thereof. In addition, the ridge canexist as a result of creasing, bending, or folding without an additionalstep of setting the ridge.

The presence of a ridge can be detected by visual observation. While thepresence of the ridge may not be particularly apparent from viewing theend of a flute due to obscuring the flute at the pleat fold, one may cutinto the filter element and see the presence of a ridge extending alonga length of a flute. Furthermore, the presence of a ridge can beestablished (in some implementations) by a technique where the filterelement is loaded with dust, and the fluted sheet peeled away to reveala cake of dust having a ridge corresponding to the ridge on the flutedmedia. The intersection of the two portions of the dust surface cakeforms an impression of the ridge, revealed as a discontinuity in thecurvature of the media. In an example implementation, the dust that canbe used to load the media to fill the flutes to provide a cake of dustwithin the flutes can be characterized as ISO Fine test dust.Impregnation of a clean filter element with a resin (such as epoxy)which is allowed to harden, and then cut into segments, is a furthereffective technique to identifying the interior geometry of a taperedflute made in accordance with the invention. Ridges, even very subtleones, can be identified using this technique.

Although ridges are very useful, it is also possible to have suitabletapered flutes with significantly fewer ridges, less extensive ridges,or no ridges at all. In some implementations less than 25% of the flutesin the pleated filtration media pack have at least one ridge betweenadjacent flute peaks. Alternatively, in some implementations less than50% of the flutes in the pleated filtration media pack comprise at leastone ridge between adjacent flute peaks. It will be understood that insome implementations at least 75% of the flutes in the pleatedfiltration media pack comprise at least one ridge between adjacent flutepeaks.

The characterization of the presence of a ridge should be understood tomean that the ridge is present along a length of the flute, but notnecessarily along the entire length of the flute. In general, the ridgecan be provided along the flute for a length sufficient to provide theresulting media with the desired performance, in particular a taperedform. While a ridge may extend the entire length of the flute, it ispossible that the ridge will not extend the entire length of the flute(100% of the flute length) as a result of, for example, influences atthe ends of the flute such as pleating or folding.

Preferably, the ridge extends at least 10% of the flute length, moretypically 25% of the flute length. By way of example, the ridge canextend at least 30% of the flute length, at least 40% of the flutelength, at least 50% of the flute length, at least 60% of the flutelength, or at least 80% of the flute length. Such ridges can extend in acontinuous or discontinuous fashion along the length of the flutes.Also, the ridges can be uniformly distributed along flutes, or can benon-uniformly positioned along the length of the flutes. For example, incertain embodiments in may be desirable to have the flutes distributedsuch that they have more or fewer ridges near either the upstream ordownstream face of a media pack. In addition, the position of the ridgeon the flute can be changed to modify taper.

For example, in some implementations at least 25% of the flutes in thepleated filtration media pack have at least one ridge between adjacentflute peaks, the ridge extending along at least 25% of the flute lengthbetween the first set of pleat folds and the second set of pleat folds.Alternatively, in some implementations at least 25% of the flutes in thepleated filtration media pack comprise at least one ridge betweenadjacent flute peaks, the ridge extending along at least 50% of theflute length between the first set of pleat folds and the second set ofpleat folds. It will be understood that in some implementations at least50% of the flutes in the pleated filtration media pack comprise at leastone ridge between adjacent flute peaks, the ridge extending along atleast 50% of the flute length between the first set of pleat folds andthe second set of pleat folds.

Alternative designs are also contemplated and within the scope of thepresent invention. For example, in some implementations at least 25% ofthe flutes in the pleated filtration media pack have ridges betweenadjacent flute peaks that extend along at least 10% of the flute lengthbetween the first set of pleat folds and the second set of pleat folds.In some implementations at least 50% of the flutes in the pleatedfiltration media pack have at least one ridge located between adjacentflute peaks and extending along at least 10% of the flute length betweenthe first set of pleat folds and the second set of pleat folds. In someimplementations at least 10% of the flutes in the pleated filtrationmedia pack contain at least one ridge between adjacent flute peaks andextending along at least 10% of the flute length between the first setof pleat folds and the second set of pleat folds.

One advantage of the present invention is that the flute geometries,typically including flute height, flute width, sharp flute peaks andoptionally one or more ridges along the flutes, allow for greateramounts of overall media surface area to be included in filtration mediapleat packs, for improved utilization of that media with minimalmasking, and tapering of the media without excessive stretching of themedia. This provides the capability to increase filter performancewithout increasing filter element size.

There is no requirement, however, that a ridge or two ridges be presentbetween every adjacent peak, or that there is a repeating pattern. Insome implementations, at least 25% of the flutes exhibit at least oneridge between adjacent peaks in order to achieve the benefits of thepresence of the ridge. Even more preferably, at least 50% of the flutes,and more preferably 100% of the flutes exhibit at least one ridgebetween each adjacent peak of the flute.

Flute Width, Height and Media Length

In addition to characterization of the flutes 310 by presence of a flutepeak 301, 303 and a ridge 308, it is possible to characterize the flutesin regard to width, height, and media length. In flute 310 of FIG. 9A,the flute width D1 is measured from the center point of the peak 302 tothe center point of the peak 304. Alternatively, the flute width D1 canbe measured from the center point of the peak 301 to the center point ofthe peak 303. With repeating regular flute geometries, these twomeasurements of D1 will be the same.

The absolute dimension of D1 will vary depending upon the application.Generally, however, D1 can scale up or down for various applications.For example, in a large diesel engine, D1 may have typical measures upto 0.5 inches or greater, with common ranges of 0.1 to 0.3 inches. In afuel filter for a small gasoline powered engine, D1 may have typicalmeasures of 0.010 inches to 0.030 inches. In a filter for a large gasturbine, D1 may typically be from 0.1 inches to 1.5 inches. These flutewidths are mere examples, and it will be understand that D1 can bevariable depending upon the application. Also, it will be understoodthat D1 can vary along the length of a flute in some implementations ofthe invention.

Yet another important dimension for the tapered flutes of the inventionis the distance J, which is the flute height, measured from the flutepeak 303 perpendicular to the plane formed by opposing peaks 302, 304.Distance J will also vary depending upon the application. Generally,however, J can scale up or down for various applications. For example,in a large diesel engine, J may have typical dimensions of from 0.03inches to 0.08 inches. In a fuel filter for a small gasoline poweredengine, J may have typical dimensions of from 0.03 inches to 0.08inches. In a filter for a large gas turbine, J may typically be from0.010 inches to 0.300 inches. In example gas turbine implementations Jis, for example, less than 0.5 inches. These flute heights are mereexamples, and it will be understand that J can be variable dependingupon the application. Also, it will be understood that J can vary alongthe length of a flute in some implementations of the invention.

The ratio of flute width to height is also adjusted in someimplementations of the invention. The flute width to height ratio is theratio of the flute width D1 to the flute height J. The flute width toheight ratio can be expressed by the following formula:flute width to height ratio=D1/J

Measured distances such as flute width D1 and flute height J can becharacterized as average values for the filtration media. Suchmeasurements can be made along the flute length excluding a certainamount (such as 20%) of the flute length at each end (due to distortionsin the flutes as a result of forming the pleat folds). Thus, thedistances D1 and J can be measured away from the ends of the flutesbecause the ends of the flutes are typically deformed as a result ofpleating. The flute width to height ratio can vary or remain over thelength of the flute. An advantage of providing a tapered flute whereinthe flute height or flute width varies over the length of the flute isthe ability to reduce potential contacts between adjacent media surfacesand thereby reduce masking.

Generally suitable D1/J ratios will be less than 10, more typically lessthan 8, and often less than 6. If D1/J becomes too high, then the flowthrough the flutes can become too restricted because the flutes are tooshort, despite being quite wide. Also, significant structuraldeformation of the flute under pressure loads becomes more likely, whichcan result in the collapse of downstream flutes. Suitable D1/J ratiosinclude greater than 1, more often greater than 1.5, and usually greaterthan 2. In most implementations the width to height ratio is at leastabout 2.0, generally at least 2.1, more typically at least 2.2, often atleast 2.3, optionally at least 2.5, and optionally at least 3.0.

Other suitable D1/J ratios include, in example implementations, greaterthan 4, greater than 6, or greater than 8. Thus, suitable rangesinclude, but are not limited to, D1/J ratios of 2 to 10, 4 to 8, and 5to 7. However, in some implementations flutes with extremely low D1/Jratios can be used (although such flutes are generally more difficult tomanufacture). For example, D1/J ratios of less than 1.0, less than 0.75,and less than 0.50 are possible. In some implementations, flutescontaining very high or very low D1/J values have better performancethan flutes containing D1/J near values of 0.5 to 2.0. Suitable rangesof such ratios for D1/J include 2 to 8 and 0.075 to 0.500.

A further dimension for characterizing geometries of a flute is thedimension D2, corresponding to the media length along the perimeter of aflute at any given spot along the flute. D2 is greater than D1 withfluted media. The length D2 is defined as the length of the fluted sheet300 for a period of the fluted sheet 300. In the case of the flutedsheet 300, the distance D2 is the length of the fluted sheet from thepeak 302 to the peak 304. This distance includes two ridges 308. Byproviding one or more ridge between adjacent peaks of the fluted media,the distance D2 can be increased relative to prior art media, resultingin increased media in a given volume. As a result of the presence of aridge or a plurality of ridges, it is possible to provide filtrationmedia having more media available for filtration compared with, forexample, pleated media not having the ridges. This is particularlyvaluable when combined with sharp flute peaks to reduce masking. Thisincrease in media can be accomplished with little, or no, increase inmasking, or even a decrease in masking. D2 is an especially usefulparameter in the design and manufacture of tapered flutes. If the D2values at different sections along the length of a pleat vary by anamount greater than the strain limit of the media, then rupture of themedia can occur. Therefore, variations in D2 along the pleat face shouldbe controlled to keep the variations within the strain limit of themedia.

An additional aspect of flute geometry of importance is the relativevalues of flute width (D1) and media length along the flute (D2). TheD2/D1 value is also useful in describing the pleated media. In someembodiments at least a portion of the flutes extending from the firstset of pleat folds to the second set of pleat folds comprises a D2/D1value that is greater than 1.0, often at least 1.05, and frequently atleast 1.1. In some implementations D2/D1 is at least 1.15, and in otherimplementations at least 1.20. A higher D2/D1 value indicates increasesin the amount of media provided along a given flute width, and can alsoresult in an increase in height J of the flute. In some implementationsD2/D1 is greater than 1.30, 1.40, or 1.50. Typical ranges for D2/D1include, for example, from 1.05 to 2.0; from 1.10 to 1.75; and from 1.20to 1.50.

Another property similar to flute width to height ratio that can providea meaningful way to understand the flutes is “open channel width heightratio.” In general, open channel width height ratio can be determinedaccording to the formula:open channel width height ratio=D1/CIn this formula, C is the open channel flute height which is the fluteheight (J) minus the media thickness (T) (See FIG. 9A). In order toenhance media performance, it is generally desirable to provide an openchannel width to height ratio greater than about 2.25, greater thanabout 2.5, greater than about 2.75, or greater than about 3. The openchannel width to height ratio is preferably less than about 10, lessthan about 9.5, less than about 9, less than about 8.5, less than about8, less than about 7.5, or less than 6. In example implementations theopen channel width to height ratio is from 2 to 7, is from 3 to 6, orfrom 4 to 5.Cord Length, Media Cord Percentage, and Media Density

While reducing masking is desirable in order to enhance filtration mediaperformance, another technique to enhance filtration media performanceis to increase the amount of media area available for filtration in agiven volume. The media configurations shown in FIGS. 9A-9C showtechniques for enhancing the amount of media surface area present in agiven volume. The media-cord percentage can help measure how a fluteconfiguration, including a tapered flute, can provide a filtration mediapack with enhanced media surface area in a given volume.

Another aspect of some implementations of the invention involves thecord length (CL) of the media to determine media-cord percentage. Cordlength refers to the straight line distance from the center point of onepeak to the center point of an adjacent peak (see, for example, adjacentpeaks 301, 302 of FIG. 9A). In order to minimize the effect of thethickness of the media, the measurement for cord length is determinedfrom a center point within the media.

The media-cord percentage requires a measurement of the cord length(CL). The relationship between the cord length CL and the media lengthD2 can be characterized as a media-cord percentage. The media-cordpercentage can be determined according to the following formula:

${{media}\text{-}{cord}\mspace{14mu}{percentage}} = \frac{( {( {{1/2}\; D\; 2} ) - {CL}} ) \times 100}{CL}$

By providing a single ridge or multiple ridges between adjacent peaks ofthe fluted media, the distance D2 can be increased relative to prior artmedia. As a result of the presence of a ridge or a plurality of ridges,it is possible to provide filtration media having more media availablefor filtration compared with, for example, pleated media not having theridges. The measurement of media-cord percentage can be used tocharacterize the amount of media provided between adjacent peaks.

The measurement of media-cord percentage can be used to characterize theamount of media provided between adjacent peaks. In example embodimentsthe media-cord percentage is greater than 1%, alternatively greater than2%, 3%, 4%, or 5%. In some implementations media cord percentage isgreater than 7.5 percent, or greater than 10 percent. Suitable rangesfor media cord percentage include, for example, from 0.1% to 15%, from0.5% to 10%, and from 1% to 5%. The media cord-percentage will notalways be the same along the entire length of a flute, thus in someimplementations of the invention, at least 25% of the flutes exhibit amedia-cord percentage of at least 1% along 50% of the flute length. Inalternative implementations at least 25% of the flutes exhibit amedia-cord percentage of at least 2%, 3%, 4% or 5% along 50% of theflute length.

The existence of increased filtration media between adjacent peaks as aresult of providing one or more ridges between adjacent peaks can becharacterized by the media-cord percentage. For the flutes made inaccordance with the present invention, the media-cord percentage can begreater than about 1%, greater than about 1.5%, and greater than about2%. In some implementations the media-cord percentage is greater than3%, and optionally greater than 4%. The media cord percentage can exceed5% in some implementations. The media-cord percentage is generally lessthan about 25%, more typically less than about 20%.

It is also desirable to have a relatively large amount of media in afilter element, provided that there is not excessive masking of themedia and that fluid flow through the media is not compromised. In thisregard an increase in media length relative to flute width (D2/D1 ),while height J remains unchanged, reflects an increase in media within agiven volume. Thus one measure of the media density within a pleatedfilter is the measure of the amount of media relative to volume. Thiscan be calculated using the formula:

$\frac{D\; 2}{( {D\; 1 \times J} )}$

Generally media density as an indicator of filter performance isoptimized by characterizing pleated media in terms of media density inaddition to other parameters.

The flute cross section shown in FIG. 9A is an example of a fluteconstructed in accordance with the invention. An alternative fluteconstruction is shown in FIG. 9B, showing fluted media 320 includingflute 330 with four ridges 328 and 329 between adjacent peaks 324 and326. Thus, a single period length of the media includes four ridges inthe depicted embodiment. It should be understood that the ridges 328 and329 are distinct from the peaks 324, 325, and 326. The media 320 can beprovided so that there are two ridges 328 and 329 between adjacent peaks(e.g., peaks 325 and 326). In the alternative, there may be three ormore ridges.

Flute 330 is similar to the flutes shown in FIGS. 5A, 5B, and 5C.Tapering of flute 330 can be accomplished by changing the positions ofthe ridges 328, 329 along the length of flute 330. Thus, if ridges 328,and 329 are slowly moved downward (away from peak 325 and toward theplane created by peaks 324 and 326), then the cross sectional area offlute 330 will gradually decrease, while the cross sectional area ofadjacent flute 332 (defined by the media between peaks 325 and 327)increases. Thus, flute 330 can be a preferred “upstream” flute thatgradually tapers down in cross sectional area until it reaches itsminimum area near the back face of the media pack, while flute 332 canbe a preferred “downstream” flute that gradually increases in crosssectional area until it reaches its maximum area near the back face ofthe media pack.

By varying the position of the ridges 328, 329 to alter the crosssectional area of the flutes 330, 332, it is possible to createsignificant taper in the flutes without changing the total length ofmedia 320 in the flutes. This is advantageous for at least two reasons:First, there is no need to waste media to create the taper, such as byrequiring some area of the media to fold over onto other areas of media.Second, formation of the tapered flutes shown in FIG. 9B by changing thelocation of the ridges 328, 329 avoids the need to significantly stretchthe media, which permits high-cellulose media and other relativelylow-stretch media to be used, such as media containing glass and ceramicfibers.

It is thus possible to taper the flutes 330 and 332 by changing theposition of the ridges 328 and 329 relative to the peaks 324, 325, and326, while simultaneously keeping the distances between the peaksrelatively constant (within the limitations of the irregularities of themedia). The height J and width D1 of the flutes 330 and 332 are notchanged along the length of the flute (in the embodiment depicted). Inthe alternative, it is also possible to create a taper that demonstrateschanges in these relative dimensions. For example, the height J of theflute 330 can be reduced along the length of the flute whilesimultaneously decreasing the distance between ridges 328 and 329.

The ridges 328, 329 can be provided as a result of the intersection ofthe relatively flatter portion of the fluted media and the relativelysteeper portion of the fluted media. The relatively steeper portion ofthe fluted media can be characterized as that portion of the flutedmedia extending between the ridge 329 and the peak 325 and can becharacterized (for example) as having an angle between the ridge 328 andthe ridge 329. Peak 325 extends above the flatter portions of the flutedmedia. Thus, the peak 325 shows a defined protrusion from the adjacentfluted media, which helps to reduce masking between flutes on adjacentpleats of media.

Now referring to FIG. 9C, fluted media 340 is depicted, and includesflutes 350 and 352. Each flute 350 includes at least two ridges 348 and349 between the adjacent peaks 344 and 345 (for a total of four ridgesper flute at the cross-section shown). Thus, along the length D2 offlute 350, the media 340 includes four ridges 348 and 349. Tapering offlutes 350 and 352 can be accomplished by moving the positions of ridges348 and 349. To increase the area under flute 350, the ridges 348 and349 are moved away from peak 345 and toward peaks 344 and 346, as shownin FIG. 9C. This results in a simultaneous diminishment in the crosssectional area of flute 352, but can be accomplished with little or noneed to stretch the media sheet 340. The tapering can also occur, forexample, by having the ridges 349 converge upon the peak 345; by havingthe ridges 348 converge on peaks 344 and 346, or by having the tworidges converge on one another.

There is no requirement that between each adjacent peak there are tworidges. There can be more than two or less than two ridges. There can bean absence of ridges between peaks if it is desirable to have thepresence of ridges alternate or provided at intervals between adjacentpeaks. However, even in the absence of ridges, it is desirable to haveeven slightly pointed peaks, such as the peak 345 shown in FIG. 9C,because such peaks can provide meaningful reductions in masking.

In general, a pattern of flutes can be provided where the pattern offlutes repeats and includes the presence of ridges between adjacentpeaks. The fluted sheets 300, 320, and 340 are shown as relativelysymmetrical from peak to peak. That is, the flutes repeat having thesame number of ridges between adjacent peaks. Adjacent peaks refer tothe peaks next to each other along a length of fluted media. A period ofmedia, however, need not have the same number of ridges between adjacentpeaks, and the media can be characterized as asymmetrical in thismanner. That is, the media can be prepared having a ridge on one half ofthe period and not having a ridge on the other half of the period.

FIG. 9A introduced the dimension D1, which is the flute width, and D2which is the media length along a flute. In typical implementations ofthe invention, D1 and D2 will remain constant along the length of aflute. However, in some implementations it is possible to change eitherD1 or D2 along the length of a flute, but such changes are typicallyoffset by opposite changes in D1 and/or D2 along the length of adjacentflutes. Thus, if one flute demonstrates a 50 percent total increase inD1 from one end to the other end of a pleat pack, it is typicallynecessary that opposite adjacent flutes demonstrate a 50 percent totaldecrease in D1 from one end to the other of the pleat pack.

If adjacent flutes do not undergo a corresponding opposite change in D1,the result is a tapered pleat pack where one face of the pleat pack willhave a larger or smaller width than an opposite face. Similarly, if oneflute demonstrates a 50 percent total increase in D2 from one end to theother end of a pleat pack, it is typically necessary that adjacentflutes demonstrate a 50 percent total decrease in D2 from one end to theother of the pleat pack. It is desirable to keep the sum of the D2measurements across the width of the media constant, otherwise the mediamust undergo significant stretching, which is generally not feasiblewith high-cellulose media. This principle by which the total medialength does not change along the pleat from one face to the other alsogenerally holds true at the pleat folds. It is necessary that the pleatfolds not require a greater cross-web media length than the width of themedia used to form the fluted media. This is true because any increasein width of the media necessary to form the flutes results in increasedstrain on the media. Although many synthetic media materials can undergomore of such strain without significant deterioration in the media,high-cellulose media do not readily undergo more than just a few percentstretching. Therefore, especially when high-cellulose media is used, itis desirable and often necessary that the pleat folds not impartsignificant stretching forces on the pleated media.

Media Volume Asymmetry & Cross Sectional Area Asymmetry

A further characteristic of the tapered media of the present inventionis the existence of media volume asymmetry in some implementations.Media volume asymmetry occurs when one side of a media pleat pack(either the upstream or downstream side) has a different volume than theother side of the media pleat pack. Such asymmetry may be created by themanner in which the flutes are constructed and how they taper. Mediavolume asymmetry, as used herein, generally measures the media volumeratio of the larger media volume bounded by the flute peaks to thesmaller media volume bounded by opposite flute peaks (see, e.g., FIGS.10 and 11A). In some, but not all implementations, the larger mediavolume corresponds to the upstream open media volume, and the smallermedia volume corresponds to the downstream open media volume (during usethe upstream volume may accumulate contaminants, such as dust).

Media volume asymmetry is beneficial for various reasons, includingimproved fluid flow and improved loading performance. In someimplementations media will demonstrate a media volume asymmetry of morethan 1%, more than 3%, more than 5%, or more than 10%. Example mediaconstructions demonstrate a media volume asymmetry of greater than 15%,greater than 20%, greater than 50%, greater than 75%, greater than 100%,greater than 150%, and greater than 200%. Suitable media volumeasymmetry ranges includes, for example, 1% to 300%, 5% to 200%; 50% to200%; 100% to 200%; and 100% to 150%. Tapered flutes may incorporatemedia volume asymmetry to further enhance filter performance.

The media pack containing tapered flutes may also demonstrate mediacross-sectional area asymmetry, which is calculated based upon across-section of the media at any given point. In a tapered flute, thecross-sectional area asymmetry will vary with measurement location alongthe depth of the fluted media pack. It will be understood thatcross-sectional area asymmetry may lead to media volume asymmetry, butthis is not always the case because tapered media cross sectional areascan be varied along the length of the flute so as to have a cumulativeeffect that the total volume on each side of the media is equal. Also, agiven cross section of a media pack may indicate a highercross-sectional area on an upstream side of the media, but subsequenttapering of the media could cause the overall media volume asymmetry tofavor the downstream side in terms of total media volume.

In some embodiments the media pack will have a cross-sectional areaasymmetry such that one side of the media has cross sectional area atleast 1 percent greater than the opposite side the same piece of media.Often the difference in cross-sectional area across the media will bemore than 3%, more than 5%, or more than 10%. Example mediaconstructions demonstrate a media cross sectional area asymmetry ofgreater than 15%, greater than 20%, greater than 50%, greater than 75%,greater than 100%, greater than 150%, and greater than 200%. Suitablemedia cross sectional area asymmetry ranges includes, for example, 1% to300%, 5% to 200%; 50% to 200%; 100% to 200%; and 100% to 150%.

The differences in cross sectional area are controlled by geometry ofthe flute design. Often the presence, number, and shape of ridges alongthe flutes significantly impacts, and often determines, the amount ofcross sectional area asymmetry. Tapering of the flutes will generallyresult in a change in the cross sectional area asymmetry along the flutelength. However, this is not always true, such as when the height J of aflute changes but the width D1 is kept constant. In such embodiments itis sometimes possible to keep the total cross sectional area constant bychanging the relative position of ridges along the flute (or otherwisechanging the distribution of the media along the flute).

Flute geometry that results in differences in cross sectional area cansignificantly impact flow properties through the flutes. Changes inrelative cross sectional area of flutes typically results in changes inthe cross sectional area of the upstream and downstream portion of themedia pack in that area: If the upstream portion of the media packundergoes an increase in cross sectional area, then the downstreamportion of the media pack will also typically undergo an decrease incross sectional area. The present invention allows for customization ofmedia volume asymmetry and cross-sectional area asymmetry to improvefilter performance.

In order to further understand what is meant by the phrase, “mediavolume asymmetry,” reference is made to FIGS. 10-12. In the case of FIG.10, the media 400 is shown fluctuating between a first theoretical plane402 and a second theoretical plane 404. The media volume asymmetryrefers to the volume differential on one side of the media 400 comparedwith the other side of the media 400 between the theoretical planes 402and 404 of the media pack. One way to characterize the theoreticalplanes 402 and 404 is to consider that the media 400 is pleated andsufficiently packed so that the peaks 406 and 408 contact opposing mediasurfaces as shown in FIG. 11 a.

The media volume asymmetry is a measure of media fluting arrangementrather than by the packing arrangement within a media pack. An opencross-sectional area on one side of the media (FIG. 10, area 407) may beseen to be extending from one surface of the media, to a line defined byflute peaks on the same side of the media. This area is greater than anopen cross-sectional area on the other side of the media (FIG. 10, area409) bounded by the opposite surface of the media, and a line defined byopposing flute peaks. These cross-sectional areas define mediacross-sectional area asymmetry for a given cross-section of media.

Extending cross-sectional area asymmetry from the upstream face to thedownstream face of the pleat pack then characterizes upstream volumesand downstream volumes and in turn, media volume asymmetry. For a pleatpack, for cases where flute peaks do or do not extend from pleat fold topleat fold, where the media between pleat folds shows little curvatureand is substantially flat (where the centroids of sections of flutes inmedia between pleat folds substantially fall on a planar surface), theupstream media volume can be seen to be the volume enclosed by theupstream media surface, the contiguous surface at the pleat folds, and aconvex hull formed over the flute peaks to center line of the pleatfolds. The downstream media volume can be seen to be the volume enclosedby the downstream media surface, the contiguous surface at the pleatfolds, and a convex hull formed over the flute peaks to center line ofthe pleat folds.

Referring now to FIG. 11A, the pleat packing arrangement shown can becharacterized as pleat count maximum (PCMax) because it represents thelargest number of pleats in a given volume wherein the flutes do notdistort each other. In FIG. 11A, a sectional view of the media 400 isshown where the media 400 is pleated back and forth upon itself. Basedupon the calculation of media volume asymmetry, the value of mediavolume asymmetry for the media arrangement shown in FIG. 11A is the sameas the media volume asymmetry for the media arrangement shown in FIG.11B, even though the peaks 406 and 408 do not touch in FIG. 11B.Accordingly, the definition of media volume asymmetry takes into accountthe potential separation between media surfaces that may exist when amedia is pleated and formed into a pleated filtration media pack.

In regard to actual measurements, the theoretical planes 402 and 404 ofFIG. 10 are determined based upon a statistical maximum peak value.Aberrations can be discarded from the calculation. For example, theremay be an occasional peak that is either too high or too low and thatdoes not significantly affect the packing density of the filtrationmedia. Those peaks are not considered for purposes of calculating thetheoretical planes 402 and 404. Furthermore, it should be understoodthat there may be occasions where peaks are skipped or formed at aheight significantly below the average flute height in order to enhancevolume asymmetry. In those cases, the reduced peak height would notaffect the packing density calculation. In general, the packing densityrefers to the number of pleats available in a given volume with just thepeaks of media surfaces touching as shown in FIG. 11A.

An advantage of calculating a “media volume asymmetry” is that thevolume of the media (the upstream volume and the downstream volume) canbe calculated based upon the media and the results can be different thanthe actual upstream and downstream volume of a filter element. Forexample, the media can be arranged as a panel where the peaksessentially just touch each other. In that case, the upstream volume anddownstream volume of a filter element should be consistent with the“media volume asymmetry” calculation.

Alternatively, however, the media can be arranged in a configurationwhere the peaks do not touch each other. For example, the media surfacescan be sufficiently separated from each other in a panel filter element,or can be separated from each other as is the typical case in acylindrical filter element. In those cases, the volume asymmetry in thefilter element is expected to be different from the “media volumeasymmetry” calculation. Accordingly, the use of the “media volumeasymmetry” calculation is a technique for normalizing the calculation ofvolume asymmetry (or volume symmetry) for a filtration media pack basedupon the media itself and irrespective of how the media is arranged orpacked in a filter element. Another calculation that can have value isthe actual volume asymmetry in a filter element. The actual volumeasymmetry for a filter element refers to the volume asymmetry resultingfrom a difference in volume between an upstream side of the element anda downstream side of the element. The arrangement of the media (e.g.,panel or cylinder) can affect this value.

Media cross-sectional area asymmetry can also be calculated byexamination of a filter element, but the cross-sectional area isdesirably measured away from the pleat folds. Thus, for example, themedia cross-sectional area can be taken along a flute length over adistance that excludes three times the flute height from the pleat fold.The reason that the media cross-sectional area asymmetry is calculatedaway from the pleat folds is to avoid the influence of the pleat foldson the media cross-sectional area asymmetry calculation. Furthermore, itshould be understood that the media cross-sectional area asymmetry mayvary along a flute length. This variation can be a result of a flutetaper.

With regard to media cross-sectional area asymmetry, the cross-sectionalarea of media will typically demonstrate asymmetry on each side of themedia. As shown in FIG. 11A, a cross section shows an asymmetry in crosssectional area 403 with cross sectional area 405.

The three dimensional structure of flutes defines an open volume forflow of fluid, as well as space for contaminants (such as dust) toaccumulate. In some embodiments the filtration media exhibits a mediavolume asymmetry such that a volume on one side of the media is greaterthan a volume on the other side of the media. In general, media volumeasymmetry refers to the volume asymmetry between an upstream side and adownstream side of pleated filtration media containing flutes. The mediavolume asymmetry is caused by the media fluting arrangement rather thanby the packing arrangement within a media pack.

Flute Density

Another technique for increasing the amount of filtration mediaavailable for filtration includes increasing the flute density of themedia pack. The flute density refers to the number of flutes percross-sectional area of filtration media in a filtration media pack. Theflute density depends on a number of factors including the flute heightJ, the flute period D1, and the media thickness T. The flute density canbe referred to as a media pack flute density, and is determined at pleatcount maximum (PCMax). PCMax is the maximum pleat count concentration atwhich the pleat pack can be manufactured without deforming the flutes.In general, PCMax refers to the maximum number of pleats that can beplaced in a given volume before performance suffers as a result ofdeformation of the flutes. For panel filters, PCMax pleat concentrationis equal to 1/(2J). The equation for calculating the media pack flutedensity (ρ) for a filter element is:

$\rho = \frac{{number}\mspace{14mu}{of}\mspace{14mu}{flutes}}{2 \times ( {{media}\mspace{14mu}{pack}\mspace{14mu}{cross}\mspace{14mu}{sectional}{\mspace{11mu}\;}{area}} )}$

The flute density of a filter element can be calculated by counting thenumber of flutes including those flutes that are upstream and thoseflutes that are downstream in a cross sectional area of the filterelement, and dividing that by two times the cross sectional area of thefilter element at the location where the number of flutes wasdetermined. In general, for regular media it is expected that the flutedensity will remain relatively constant across the length of the filterelement from the inlet face to the outlet face, or vice versa.

It should be understood that the media cross sectional area refers tothe cross sectional area of the media and not necessarily to the crosssectional area of the filter element. The filter element may have asheath or a seal intended to engage a housing that would provide thefilter element with a cross-sectional area that is greater than thecross-sectional area of the media. Furthermore, the cross-sectional areaof the media refers to the effective area of the media pack, and doesnot include portions of the media pack not useful for filtration (suchas areas obscured by the seal).

In general, providing a media pack having increased flute density has atendency to increase the surface area of media within a volume of themedia and, therefore, has a tendency to increase the loading capacity ofthe filtration media. Accordingly, increasing the flute density of mediacan have the effect of enhancing the loading capacity of the media.However, increasing the flute density of media can have the effect ofincreasing the pressure drop through the media assuming other factorsremain constant.

Increasing the flute density of filtration media often results fromdecreasing the flute height (J) or the flute period length (D1), orboth. As a result, the size of the flute (the size of the flute refersto cross sectional area of the flute) decreases as flute densityincreases. Smaller flute sizes can have the effect of increasing thepressure drop across the filtration media pack. The reference to apressure drop across the media pack refers to the pressure differentialdetermined at a first face of the media pack relative to the pressuremeasured at a second face of the media pack, wherein the first face andthe second face are provided at generally opposite sides of the mediapack. The pressure drop across the media pack depends, in part, on theflute density and the flute length.

Now referring to FIGS. 12-14, a pleated filtration media pack is shownat reference number 450. The pleated filtration media pack 450 includesmedia 452 having a machine direction 454 and a transverse direction 456.The media is folded to provide a first series of pleat folds 458 and asecond series of pleat folds 459 (see FIG. 12 for folds 458 and 459),wherein the media 452 extends in a back and forth arrangement betweenthe first set of pleat folds 458 and a second set of pleat folds 459.The media 452 includes flutes 470. The flutes 470 include relativelysharp peaks 472 and 474. In addition, the flutes 470 include ridges 476provided between adjacent peaks (e.g., peaks 472 and 474).

The pleated filtration media pack 450 includes media surfaces 482 and484 that form openings 486 there between, and media surfaces 488 and 490that form openings 492 there between. The pleated filtration media pack450 can be characterized as having a first face 485 that includes thefirst set of pleat folds 458 and the openings 486. In addition, thepleated filtration media pack 450 can be characterized as having asecond face 487 that includes the second set of pleat folds 460 and theopenings 492. Accordingly, air can flow into the pleated filtrationmedia pack 450 via the openings 486 in the first face 492, pass throughthe media 452 to provide filtration, and then flow out of the pleatedfiltration media pack 450 via the openings 492 in the second face 494.In certain circumstances, it may be advantageous to have the fluid flowinto the pleated filtration media pack via the second face 494 and outof the pleated filtration media pack 450 via the first face 485. Themedia includes ridges 493 which are converging together. This taper isforeshortened, showing an exaggerated movement of the ridges.

Referring now to FIGS. 15 and 16, top plan views of portions of twomedia arrangements made in accordance with the present invention aredepicted. In FIG. 15, a simplified drawing of a web of filtration media500 is shown with a depiction of the location of the portions of eachflute, but before flute formation and pleating (thus, FIG. 15 showsfilter media 520 in a flattened state that depicts where flute peaks andridges are to be located during flute formation). The outline of each ofthe flutes 502 includes central peaks 504 and adjacent opposite-sidepeaks 506. Locations of subsequent pleats are shown by lines 510. Theembodiment shown in FIG. 15 is shown with six flutes 502. Each of theflutes 502 includes four ridges 508 a and 508 b in dashed lines. Theridges are positioned such that one pair of ridges 508 a and 508 b areon each side of peak 504 of each flute 502. The ridges 508 a and 508 bconverge toward one another to create a flute similar to that shownearlier in FIG. 7. Thus, on each side of each peak 504 is a pair ofridges 508 a and 508 b that converge upon one another along one pleat,then diverge from one another along the next pleat, and again convergeupon one another in the subsequent peak. In this way it is possible tochange the cross sectional area of the pleated media using thefiltration media 500. It will be observed that in FIG. 15 the centralpeaks 504 and adjacent opposite-side peaks 506 are parallel to oneanother, which allows for creation of fluted media wherein the fluteshave a constant width and height, while still having a change in crosssectional area along their length.

With regard to FIG. 16, media 520 is shown with a plurality of flutesdefined by center peak 524 and adjacent opposite-side peaks 526. Pleatlocations 530 are also depicted. The media shown in FIG. 16 isflattened, depicting the locations of the peak 524 and adjacentopposite-side peaks 526. In this embodiment the flutes do not haveparallel peaks 524, 526. Thus, the media can be used to create taperedflutes while varying the width or height of the flutes. In theembodiment shown in FIG. 16, no ridges are necessary to create thetapered fluted media.

Flute Peak Radius

As noted above, the flute peaks are typically characterized by a sharpradius or a defined tip that reduces masking between pleats. Thisdefined tip can extend from the general profile of the flute to create aprotrusion at the flute peak that substantially reduces masking ofadjacent media. While it will be understood that a given flute peak willhave some variation in shape, and not necessarily form a perfect arc atits tip, it is still possible in some implementations to identify andmeasure a distance that corresponds substantially to a radius at theflute peak. This radius can be measured on the interior of the flute andis calculated as the effective inner radius. This effective inner radiuswill often be less than 4 millimeters, more often be less than 2millimeters, frequently be less than 1 millimeter, and optionally lessthan 0.5 mm. Larger radii can also be used in some implementations,especially for large flutes. It will further be understood that flutesthat fail to have a distinct or measurable radius still fall within thescope of the disclosure when they contain other characteristicsdescribed herein, such as the presence of ridges, media asymmetricvolumes, etc.

FIG. 17 shows an example of a radius determined on actual filter media.Radii can be measured, for example, by a methodology that uses a measurecalled the local effective inner radius. Local effective inner radius isdefined as the minimum outer radius of curvature at a given flute tip,peak, or ridge, minus the average media thickness of the flute. Theminimum outer radius of curvature is the smallest radius of curvature ofan osculating circle fitting the curve formed by following the outermostsurface of a cross section of a given flute tip, peak, or ridge. Forreference, the osculating circle of a sufficiently smooth plane curve ata given point on the curve is the circle whose center lies on the innernormal line and whose curvature is the same as that of the given curveat that point.

In the alternative, a formula that can be used to describe an acceptableradius (for certain embodiments) is based on flute width (D1) and mediathickness (T). An example formula that can be used to describe theradius at the peak that can be characterized as a relatively sharpradius is (D1−2T)/8. Preferably, a relatively sharp radius has a radiusof less than about (D1−2T)/16.

Although the peaks are sharp, in many implementations they still containa tightly curved outer surface, sometimes approximating an arc or a bendwith a radius. By providing relatively sharp peaks, the area of contactand/or proximity between media surfaces may be reduced, which results ina reduction in masking During filtration the filtration media willtypically deflect under pressure, and the relatively sharp peaks cancontinue to reduce the contact between media surfaces, thus providing anongoing advantage with regard to reduction of masking.

A method of filtering a fluid is also provided according to theinvention. The method includes a step of passing a fluid through apleated filtration media pack provided as part of a filter element as aresult of unfiltered fluid entering the first face or the second face ofthe pleated filtration media pack and out the other of the first face orthe second face of the pleated filtration media pack. The flow of thefluid to be filtered through the pleated filtration media pack can becharacterized as straight through flow.

Flute Orientation

It may be advantageous to have the flutes extending at anon-perpendicular angle relative to the first flow face or the secondflow face depending upon whether the fluid is flowing toward the firstface or the second face at an angle that is non-perpendicular. Byproviding the flutes at a non-perpendicular angle relative to the firstface or the second face of the pleated filtration media pack, it ispossible to enhance the flow of the fluid into the pleated filtrationmedia pack by adjusting the flute angle to better receive the fluid flowwithout the fluid having to make a turn before entering the pleatedfiltration media pack. The first face and the second face of the mediapack can be parallel or non-parallel. The angle at which the flutesextend can be measured relative to the first face, the second face, orboth the first face and the second face.

Thus, the flutes can be formed so that they extend perpendicular to thefirst face or the second face, or can be provided extending at an anglerelative to the first face or the second face that is greater than 0degrees but less than 180 degrees. If the flutes extend at an angle of 0degrees or 180 degrees to a face, then it is difficult for fluid toenter the pleated filtration media pack via the flutes. In general, itis desirable for the fluid to enter the pleated filtration media pack byentering through the flutes.

In some implementations the flutes will extend from about 85 degrees to95 degrees to a face, in other implementations from about 60 to 120degrees to a face, and in yet other implementations from about 70 to 110degrees to a face. Preferably, the flutes are provided extending at anangle that is within about 60 degrees of perpendicular to the first faceor the second face. In general, this range corresponds to about 30degrees to about 150 degrees relative to the first face or the secondface. Furthermore, the flutes can be provided extending within about 5degrees of perpendicular to the first face or the second face(corresponding to about 85 degrees to about 95 degrees relative to thefirst face or the second face). The flutes can desirably be providedextending perpendicular (90 degrees) relative to the first face or thesecond face.

Methods of Making Pleated Media with Flutes

Pleated media containing flutes can be produced using various methodsand equipment. Thus, the media, media pleat packs, and filter elementsare not limited to their methods of manufacture. Fluted media can beprepared by any technique that provides the desired flute shapes. Thus,the invention is not limited to specific methods of forming the flutes.However, depending upon the flute geometry and the media being flutedand pleated, certain methods will be more or less successful. Dry mediawith high cellulose content is relatively non-stretchable, and issubject to tearing if it is stretched beyond just a few percent. Incontrast, media with a high synthetic content is often much morestretchable. Both types of media are suitable for use with theinvention.

During media formation, the limited dimension of the media is typicallythe width of the media because the machine on which the media ismanufactured is limited in the width direction. The length of the mediacan be continuous until it is cut or until it ends. The continuousdirection refers to the direction of the media along the length of themedia. The transverse direction generally refers to the direction of themedia across the width of the media. Pleated media generally includespleats or folds formed transversely to the machine direction so that thenumber of pleats and the height of each pleat can be controlled, asdesired. Pleats or folds are typically formed in the transversedirection such that the media folds back upon itself in an alternatingfashion (e.g., a back and forth arrangement) to form a filter elementhaving a first face, a second face, and an extension of media betweenthe first face and the second face. In general, fluid to be filteredenters one of the first face and the second face of the filtration mediapack, and exits the other of the first face and the second face.

Exemplary techniques for providing fluted media exhibiting relativelysharp peaks include bending, folding, or creasing the fluted media in amanner sufficient to provide a relatively sharp edge. The ability toprovide a relatively sharp peak depends on a number of factors,including the composition of the media itself and the processingequipment used for providing the bend, fold, or crease. In general, theability to provide a relatively sharp peak depends on the rupturestrength and thickness of the media and whether the media containsfibers that stretch or resist tearing or cutting. It is desirable toavoid tearing, cutting, or otherwise damaging the filtration mediaduring flute forming.

The present method can utilize media that can only handle a relativelysmall amount of strain because the pleat folds are formed to keepoverall media length relatively constant and reduce strain. In general,media that can tolerate only a relatively small amount of strainincludes media that has tendency to rupture when the strain is greaterthan as little as 3%, such as is often the case for media that has ahigh cellulose content and is cold and dry. Even wet, warm media willoften have a tendency to rupture when the strain is greater than about8% with some media, and about 10% in other media, or occasionallygreater than about 12%. Thus, the flute designs and methods ofmanufacture of the present invention can be used, in someimplementations, with media that has high cellulose content. In someembodiments the cellulose content is at, or near, 100%. In otherimplementations the cellulose content is greater than 90%, 80%, 70%, 60%or 50%.

As shown earlier, the total media width can be made constant across thetransverse direction of the pleats. This allows for a pleat foldconfiguration that results in an overall strain on the media that isrelatively small. Accordingly, the media that can be used in thefiltration media pack can be characterized as media not capable ofwithstanding strain of greater than about 8% in some implementations,10% in other implementations, or greater than about 12% in yet otherimplementations. However, it will be understood that media able towithstand high levels of strain can also be used with variousimplementations of the invention.

FIG. 18 depicts one system 600 for forming pleated media consistent withthe technology disclosed herein. A roll of media 620 is on an unwindstand 622 in communication with bunching mechanism 640 to bunch themedia 602. The media 602 is passed through bunching mechanism 640 toshaping rolls 660 and scoring rolls 670 to be shaped and scored,respectively. After exiting the shaping rolls 660 and scoring rolls 670,the media 602 optionally passes through a coating station 675 and entersa reefing section 680, where it is folded along the scores and stored inpacked segments 612.

The media roll 620 is used to store the media 602 until processing, andgenerally arrives at the processing location in such a configuration.The roll of media 620 can include a variety of types of media 602 thatis wound on the roll 620. Generally, the media 602 will be a flat,relatively flexible sheet such that it is capable of being wound andunwound. The media 602 is, in a variety of embodiments, a cellulosemedia, although other types of media are also contemplated. For example,the media 602 could also be a synthetic media such as a flat sheet of apolymeric media.

FIGS. 19A and 19B depict a top view and a side view, respectively, ofthe media as it passes through a system similar to that depicted in FIG.18. The first section 692 represents the media after it leaves the mediaroll 620 and is introduced to the system. The second section 694 depictsthe media generally after it exits processing by the bunching roll 640,which is represented by the first vertical sectioning line. The thirdsection 696 represents the media 602 after exiting the shaping andscoring rolls 660, and the fourth section 698 represents the media 602upon entering the reefing section 680 of the system.

“Bunching” is used to refer to a process undergone by the media 602, andalso a physical state of the media 602, as depicted in the secondsection 694 of FIGS. 19A and 19B. The media 602 displays substantiallyparallel undulations 604 along the length of the media 602 where thelength of the media 602 is generally in the machine direction, in otherwords, the direction parallel to the passage of the media 602 throughthe various system components. Bunching 640 avoids generation of strainin the media 602 as it is being fluted, which results in increased media602 tolerance to creating flutes and otherwise shaping the media. As aresult of bunching the media 602, the width of the media 602 decreasesslightly and the height of the media 602 increases slightly as theundulations are created. The bunching mechanism can have a variety ofconfigurations, and will be described in more detail by way of examplein the description of FIG. 20, below.

Following bunching 640 of the media, the media can be shaped 660 andscored, as depicted in section 696 of FIG. 19A and FIG. 19B. “Shaping”forms flutes 606 in the machine direction along the length of the media602, and “scoring” forms fold-lines 608 in the media 602, perpendicularto the flutes 606—which is generally in the cross-machine direction. Thescore 608 generally has a unique shape that corresponds to the shape ofthe flutes 606. In one embodiment, the media 602 passes between two niprollers, and then passes between two scoring rolls. In anotherembodiment the media passes between two nip rollers that define ascore-bar. Shaping and scoring the media will be described in moredetail, below.

Adhesive can be applied in a variety of embodiments after the media isshaped and scored, which is not visible in FIG. 19A or 19B, butcorresponds to coating rollers 675 of FIG. 18. The adhesive applicationputs a small amount of adhesive material at a point along the flute tipsso that it can be bonded to another flute that touches it after themedia is folded. The glue or adhesive material (various adhesives can beused, including hot-melt adhesives, hot-set adhesives, etc.) ispreferentially applied in a manner so as to avoid excessively sealingthe media by application of the glue or bonding material. For example,reference can be made to earlier FIG. 11A, which shows flute tips 406and 408 in contact with flutes on adjacent pleats. Adhesive can beapplied at these locations (such as where flutes come together at tips406 or 408). Generally the amount of adhesive present must be sufficientto hold the pleats together during production as well as during use.Thus, a strong bond between adjacent pleats is normally necessary whenan adhesive is used. In some embodiments the adhesive runs along theentire flute tips, but in other implementations the adhesive runs onlyalong a portion of each flute tips. For example, the adhesive can beapplied intermittently along the flute tips, can be applied primarilynear the pleat folds, can be applied only to a fraction of the pleattips, etc. In addition to the use of adhesive material to bond taperedflutes, it will be understood that non-tapered (i.e., regular) flutescan also be bonded together using adhesive material.

The media may also come into contact with a coating roll 675 toadminister adhesives or other coatings. Following coating or, in thealternative, following shaping and scoring, the media enters the reefingsection 680. The reefing section 680 is where the media 602 is foldedalong the score lines 608 in an accordion-like fashion, and stored assuch until further processing. As more media 602 is processed throughthe system 600 and introduced into the reefing section 680, the media602 becomes more packed and the compresses about the score lines 608.

Now components of the system 600 of FIG. 18 will be described in moredetail. FIG. 20 depicts a bunching mechanism consistent with thetechnology disclosed herein. In at least one embodiment the bunchingmechanism 640 has a primary roll 642 and a plurality of bunching axles650 about the circumference of the primary roll 642, in mechanicalcommunication with the primary roll 642. Each of the plurality ofbunching axles 650 are configured to rotate about their respective axis.Each axis 651 of the plurality of bunching axles 650 can be rotatablydisposed about the circumference of the primary roll 642. In theembodiment depicted, the plurality of bunching axles 650 are rotatablydisposed on a first axle holder 644 and a second axle holder 646 on eachside of the primary roll 642. The first axle holder 644 and the secondaxle holder 646 define openings that are configured to receive each endof each axle of each of the plurality of bunching axles. In thealternative, the bunching mechanism can comprise a series of rollers ina substantially planar arrangement (as opposed to the circulararrangement of FIG. 20) whereby media is bunched progressively as itpasses from a first roller to a last roller.

FIG. 21 depicts the media 602 entering the bunching mechanism 640,leaving the bunching mechanism 640 bunched, and entering a pair ofshaping rollers 660. The following description of the bunching mechanismcan be understood in view of FIG. 20 and FIG. 21. In operation, themedia is fed onto the circumference of the primary roll 642 and isprogressed through the primary roll 642 and each of the plurality ofbunching axles 650 separately, where each of the plurality of bunchingaxles 650 introduces two undulations: one undulation adjacent to eachside of the media, which incrementally and progressively bunches themedia. The exception to this is the first bunching axle 652, whichintroduces a single, first undulation along a central portion of themedia.

As just mentioned, the media is first passed over the primary roll 642and a first bunching axle 652, where the first bunching axle 652 definesa first bunching shape 653. The first bunching axle 652 is cylindricaland rotates about a central axis 651. The first bunching shape 653defined on the first bunching axle 652 exerts force on the media as itpasses between the first bunching shape 653 and the primary roll 642,which creates a first undulation along the central portion of the media.As such, the surface of the remainder of the first bunching axle 652likely does not make contact with the media. In the current embodiment,the first bunching shape 653 is a single rounded, circular diskextending radially from the first bunching axle. The first bunchingshape 653 has a first bunching width and is positioned substantiallycentral to the width of the media.

After passing through the primary roll 642 and the first bunching axle,the media then passes through a second bunching axle 654 and the primaryroll 642. The second bunching axle 654 defines a second bunching shape655 having a second bunching width, where the second bunching width isgreater than the first bunching width. The second bunching shape 655includes the first bunching shape 653 and also includes an addition tothe first bunching shape such that bunching the media is incrementallyprogressed. As such, the second bunching shape 655 has the circular diskof the first bunching shape 653, to engage and enforce the firstundulation along the media, and a pair of circular disks that are eachadjacent to opposite sides of the first bunching shape 653. The secondbunching shape 655, and, accordingly, the second bunching width, ispositioned substantially central to the width of the media. Also, thecentral disk of the second bunching axle 654 is substantially co-radialwith the central disk of the first bunching axle 652 such that thecentral disk of the second bunching axle 654 and the disk of the firstbunching axle 652 both engage the first undulation of the media.

Following passage of the media between the second bunching axle 654 andthe primary roll 642, the media passes between a third bunching axle 656and the primary roll 642. The third bunching axle 656 defines a thirdbunching shape 657 having a third bunching width greater than the secondbunching width. The third bunching shape 657 and accordingly, the thirdbunching width, is positioned substantially central to the width of themedia. The third bunching shape 657 includes the three disks of thesecond bunching shape 655, and then two additional disks: one adjacentto each side of the second bunching shape 655, respectively. The threecentral disks of the third bunching shape 657 are generally co-radialwith the disks of the second bunching shape 655.

The media is then passed between a fourth bunching axle 658 and theprimary roll 642, where the fourth bunching axle 658 defines a fourthbunching shape 659 having a fourth bunching width greater than the thirdbunching width and is positioned substantially central to the width ofthe media. The fourth bunching shape 659 is the five disks of the thirdbunching shape 657, and then two additional disks: one adjacent to eachside of the third bunching shape, respectively.

The media can then be passed between the primary roll 642 and anyadditional number of bunching axles 650, depending on the width of theroll to be bunched, as each bunching axle after the first bunching axleincreases the width of the bunched portion of media by a particularincrement, namely, the width of two additional bunching disks. The fivecentral disks of the fourth bunching shape 659 are generally co-radialwith the disks of the third bunching shape 657.

Each incremental bunching axle of the plurality of bunching axles 650includes the shape of the bunching axle preceding it to engage andenforce the existing shape of the media. Each of the plurality ofbunching axles 650 adds an incremental addition to the shape of thebunching axle before it, to incrementally progress the bunching of themedia. The bunching disks generally have a particular radius such thatthat depth and width of each undulation on the media is substantiallyconsistent along the length of the media. Each disk is generallyidentical and equally spaced such that bunching is substantiallyconsistent across the width of the media.

As the number of bunching axles increase, it may be desirable to use aprimary roll 642 of a larger diameter to accommodate the plurality ofbunching axles about the circumference of the primary roll. As such, asystem could have multiple primary rolls that can be switched andchanged depending on the width of the media to be bunched.

As mentioned above, bunching the media 602 can increase the straintolerance of the media to withstand further shaping and processing. Assuch, after the media is bunched, it can be further shaped by othercomponents of the system, such as the nip rollers 660 as depicted inFIG. 21. FIG. 22 also depicts a pair of nip rollers 660 to shape themedia. In a variety of implementations, shaping the media includesforming flutes along the length of the media.

The media is generally fluted by passing between two nip rollers 660after bunching the media 602. The nip rollers 660 impress the shape ofthe flutes along the length of the media as the media passes between therollers 660. As such, the nip rollers 660 define the desired shape ofthe flutes. A first nip roller 666 of the pair of nip rollers 660 candefine a particular flute shape 664, and a second nip roller 668 of thepair of nip rollers 660 can define a mating flute shape 662, such thateach side of the rollers 660 enforces the same flute shape on the media.In another embodiment the mating flute shape 662 could be a pliablesurface to receive the particular flute shape 664.

The flutes are generally established in the machined direction of themedia. In some embodiments, the media is heated (such as by steam,infrared heaters, heated rollers, etc.) before or while it passesthrough the nip rollers 660, and cooled after the shaping process. Assuch, the nip rollers 660 can be heated in at least one embodiment. Theflutes can have a variety of configurations. In one configuration theflutes are tapered. In another configuration the flutes aresubstantially straight. In yet another configuration the flutes arepartially tapered.

In another embodiment, the media is shaped and scored with nip rollers.FIG. 23 depicts nip rollers 760 where a first nip roller 766 hasplurality of score-bars 772 and a second nip roller 768 having aplurality of scoring surfaces 770 that are each configured to receiveeach of the respective score-bars 772. The scoring surfaces 770 cancomprise a compressible material in one embodiment. In anotherembodiment, the scoring surfaces 770 are openings defined by the secondnip roller 768 that accommodate the shapes of each of the respectivescore-bars 772. In yet another embodiment, the scoring surfaces 770 arefemale mating surfaces that accommodate the shapes of each respectivescore-bar 772.

Scoring the media generally results in bending the media at intervals inthe cross-machine direction where the media will be folded. As such, ascore-bar 772 can be used to “stamp” across the width of the media atintervals where the media will be folded. The profile of the score-bar772 generally follows the profile of the local flutes. So, for example,with a media having tapered flutes, the score-bars 772 are tall wherethe local flutes are tall, and the height of the score-bar 772 decreaseswhere the height of a local flute decreases.

As the media is generally folded accordion-style, such that it is firstfolded to a particular width, and then folded back on itself again, themedia is consecutively scored from alternate sides. As such, thescore-bars 772 and score surfaces 770 generally alternate consecutivelyon the surfaces of the nip rollers 760, such that both the first niproller 766 and the second nip roller 768 have a plurality of score-bars772 and a plurality of scoring surfaces 770. As depicted on FIG. 23, ascore-bar 772 on the second nip roller 768 mates with a scoring surface770 on the first nip roller 766.

In at least some embodiments of the technology described herein, the niprollers can be altered to create various shapes of media. In suchembodiments it can be desirable to have a nip roller than includesmultiple components that can be replaced and changed according to theresultant shape of the media that is desired. FIG. 24 depicts oneexample segmented nip roller 866 having interchangeable and switchablecomponents (showing the roller 866 in exploded view). The nip roller 866has a roller base 867 that generally defines the shape of the roller,and provides a surface to which to couple other components. A pluralityof segments 865 communally define the flute shape 864 that will beimpressed on the media. Alternating score-bars 872 and score surfaces870 extend at circumferential intervals across the width of the roller.

FIG. 25 depicts a cross-sectional view of the segmented nip roller 866of FIG. 24, which provides a profile view of a portion of the fluteshape 864 on a particular segment 865. FIG. 26 depicts a perspectiveview of the segment 865 depicted in FIG. 25. The segment 865 defines acoupling surface 869 by which the segment 865 is coupled to the niproller 867. In a variety of implementations, segments 865 and score-bars872 can be exchanged, interchanged, removed, and replaced to change theresultant media shape. In at least one embodiment the segments 865and/or score-bars 872 are bolted, screwed, or otherwise fastened intoplace on the roller base 867. In another embodiment the segments and/orthe score-bars are frictionally held into place through a snap-infixture defined by the roller base 867, the segments 865 and/orscore-bars 872, or both. In at least one embodiment, alignment pins arereceived by each segment 865 and the nip roller 867 to ensure properplacement.

FIGS. 27a, 27b, and 27c are cross sectional schematics demonstratingvarious spacing of the score-bars on the segmented nip roller 866 ofFIG. 24. While these schematics depict segments 865 that are largelyuniform, it can be possible to have segments 865 of varying widths.

FIG. 28 depicts another system consistent with the technology disclosedherein, incorporating a nip roll 860 that both shapes and scores themedia. A roll of media 820 is on an unwind stand 822 in communicationwith a bunching mechanism 840 to bunch the media 802. The media 802 ispassed through the shaping and scoring rolls 860 to shape and scorerolls. After the media passes over the shaping and scoring rolls 860 itmay also come into contact with a coating roll to administer adhesivesor other coatings. After exiting the shaping and scoring rolls the mediaenters the reefing section 880, where it is folded along the scores andcan be cut into media pleat packs.

An alternative bunching and shaping mechanism of FIG. 29 will bedescribed. As described above, media is fed to pass over thecircumference of a primary roll 946, and is gradually bunched as themedia progresses about the primary roll 946. The primary roll 946 isgenerally configured to receive the media. A first bunching and formingroll 941 is positioned at the circumference of the primary roll 946 andcentral to the width of the primary roll 946. In multiple embodimentsthe first bunching and forming roll 941 is also positioned such that itwill be central to the width of the media passing over the primary roll.The media is passed between the primary roll and the first bunching andforming roll 941 such that forces exerted on the media from the firstbunching and forming roll 941 results in a flute along the length of themedia.

After the media passes through the first bunching and forming roll 941and the primary roll 946, it then passes through a pair of secondbunching rolls 942, which are also positioned at the circumference ofthe primary roll 946. The distance between the second bunching andforming rolls 942 is greater than the width of the first bunching andforming roll 941, and the second bunching and forming rolls 942 areconfigured to exert forces on the media resulting in a flute along thelength of the media on each side of the flute resulting from passingunder the first bunching and forming roll 941. A pair of third bunchingand forming rolls 943 and a pair of fourth bunching and forming rolls944 are also positioned at the circumference of the primary roll 946,and are configured to exert forces of the media resulting in a flutealong the length of the media on each side of the existing flutes. Assuch, the distance between the third bunching and forming rolls 943 islarger than the distance of the second bunching and forming rolls 942,and the distance between the fourth bunching 944 rolls is larger thanthe distance between the third bunching and forming rolls 943. The firstbunching and forming roll 941 is generally substantially central to thedistance between the second bunching and fluting rolls 942, thirdbunching rolls 943, and fourth bunching and fluting rolls 944.

In a variety of embodiments there is a pair of fifth bunching andfluting rolls, a pair of sixth bunching and fluting rolls, and a pair ofseventh bunching rolls. In general, as many pairs of bunching rolls areimplemented along the circumference of the primary roll as are needed tobunch media of a particular width. In at least one embodiment there are50 pairs of bunching rolls.

Filtration Media

The filtration media can be provided as a relatively flexible media,including a non-woven fibrous material containing cellulose fibers,synthetic fibers, glass fibers, ceramic fibers, or combinations thereof,often including a resin therein, and sometimes treated with additionalmaterials. An example filtration media can be characterized as acellulosic filtration media that can tolerate about up to twelve percent(12%) strain without tearing when wet and warm, but which will ruptureat lower percent strain when dry and cold (as low as 3% with somemedia). The filtration media can be fluted into various fluted shapes orpatterns without unacceptable media damage and can be pleated to formpleated filtration media. In addition, the filtration media is desirablyof a nature such that it will maintain its fluted configuration, duringuse. While some filtration media is available that can tolerate greaterthan about twelve percent (12%) strain, and such media can be usedaccording to the invention, that type of media is typically moreexpensive because of the need to incorporate relatively large amounts ofsynthetic fibers.

In the fluting process, an inelastic deformation is caused to the media.This prevents the media from returning to its original shape. However,once the forming displacements are released, the flutes will sometimestend to spring partially back, maintaining only a portion of the stretchand bending that has occurred. Also, the media can contain a resin.During the fluting process, the media can be heated to soften the resin.When the resin cools, it will help to maintain the fluted shapes.

The filtration media can be provided with a fine fiber material on oneor both sides thereof, for example, in accord with U.S. Pat. Nos.6,955,775, 6,673,136, and 7,270,693, incorporated herein by reference intheir entirety. In general, fine fiber can be referred to as polymerfine fiber (microfiber and nanofiber) and can be provided on the mediato improve filtration performance. The fine fiber can be added atvarious stages of the manufacturing process. For example, in someimplementations the media will contain fine fiber before the flutes areformed, while in other implementations the fine fiber is added as alayer or layers to the fluted media. As a result of the presence of finefiber on the media, it can be possible to provide media having a reducedweight or thickness while obtaining desired filtration properties.Accordingly, the presence of fine fiber on media can provide enhancedfiltration properties, provide for the use of thinner media, or both.Exemplary materials that can be used to form the fine fibers includepolyvinylidene chloride, polyvinyl alcohol polymers, polyurethane, andco-polymers comprising various nylons such as nylon 6, nylon 4,6, nylon6,6, nylon 6,10, and co-polymers thereof, polyvinyl chloride, PVDC,polystyrene, polyacrylonitrile, PMMA, PVDF, polyamides, and mixturesthereof.

Several techniques can be relied upon for enhancing the performance ofpleated filtration media. The technique can be applied to pleatedfiltration media used in panel filter arrangements and for pleatedfiltration media used in cylindrical or conical filter arrangements.Depending on whether the pleated filtration media is intended to be usedin a panel filter arrangement or a cylindrical or conical filterarrangement, alternative preferences can be provided. In view of thisdisclosure, one would understand when certain preferences are moredesirable for a panel filter arrangement and when certain preferencesare more desirable for a cylindrical filter arrangement.

Accordingly, it should be understood that the identification of apreference is not intended to reflect a preference for both panel filterarrangements and cylindrical filter arrangements. Furthermore, it shouldbe understood that the preferences may change as a result of whether thecylindrical filter arrangement is intended to be an arrangement that canbe characterized as a forward flow arrangement (where dirty air flowsinto the filter media pack from the exterior cylindrical surface) or areverse flow filtration media pack (where dirty flows into thefiltration media pack from the inner surface of the filtration mediapack).

Pleat Pack and Filter Element Configurations

Filter elements are also provided according to the invention, the filterelements incorporating media having flutes. Filter elements are providedthat can include a pleated filtration media pack and a seal arrangedrelative to the filtration media pack so that fluid to be filteredpasses through the filtration media pack as a result of entering inthrough one face of the media pack and out the other face of the mediapack. The seal can be attached directly to the pleated filtration mediapack or indirectly via a seal support, and can be provided to engage ahousing to provide a seal between the housing and the filter element.The seal can be provided as an axial seal, a radial seal, or acombination axial and radial seal. Crimp seals, pinch seals, and manyother forms of seals are also possible.

A filter element or filter cartridge can be provided as a serviceablefilter element. The term “serviceable” in this context is meant to referto a filter element containing filtration media where the filter elementcan be periodically removed and replaced from a corresponding aircleaner. An air cleaner that includes a serviceable filter element orfilter cartridge is constructed to provide for the removal, cleaning,and replacement of the filter element or filter cartridge. In general,the air cleaner can include a housing and an access cover wherein theaccess cover provides for the removal of a spent filter element and theinsertion of a new or cleaned (reconditioned) filter element.

A pleated filtration media pack formed into a panel can be referred toas a “straight through flow configuration” or by variants thereof whenthe faces on the pleated filtration media are parallel. For example, afilter element provided in the form of a panel generally can have aninlet flow face and an exit flow face, with flow entering and exitingthe filter element in generally the same straight through direction. Insome instances, each of faces can be generally flat or planar, with thetwo parallel to one another. However, variations from this, for examplenon-planar faces, are possible in some applications.

Alternatively, the inlet and outlet flow faces can be provided at anangle relative to each other so that the faces are not parallel. Inaddition, a filter element can include a filtration media pack having anon-planar face, and a non-planar face can be considered non-parallel toanother face. An exemplary non-planar face for a filtration media packincludes a face that forms the interior surface or the exterior surfaceof a filtration media pack formed in a cylindrical arrangement or in aconical arrangement. Another exemplary non-planar face for a filtrationmedia pack includes a filtration media pack wherein the media surfaceshave an inconsistent or irregular pleat depth (e.g., the pleat depth ofone pleat is different from the pleat depth of another pleat). The inletflow face (sometimes referred to as “end”) can be referred to as eitherthe first face or the second face, and the outlet flow face (sometimesreferred to as “end”) can be referred to as the other of the first faceor the second face.

A straight through flow configuration found in filter elementscontaining pleated filtration media formed into a panel is, for example,in contrast to cylindrical filter elements containing pleated filtrationmedia arranged in a cylindrical configuration of the type shown in U.S.Pat. No. 6,039,778, in which the flow generally makes a substantial turnas its passes through the filter element. That is, in a filter elementaccording to U.S. Pat. No. 6,039,778, the flow enters the cylindricalfilter cartridge through a cylindrical side, and then turns to exitthrough a cylindrical filter end in a forward-flow system. In areverse-flow system, the flow enters the cylindrical filter cartridgethrough an end and then turns to exit through a side of the cylindricalfilter cartridge. An example of such a reverse-flow system is shown inU.S. Pat. No. 5,613,992. Another type of filter element containingpleated filtration media can be referred to as a conical filter elementbecause the filtration media pack is arranged in a conical form.

Now referring to FIGS. 30 and 31, a portion of a filtration media packis shown at reference number 1000 in a partial cylindrical arrangement.The filtration media pack includes a first face 1004 and a second face1006. For the cylindrical arrangement 1000, the first face 1004 can beconsidered the inner surface of the cylindrical arrangement, and thesecond face 1006 can be considered the outer surface of the cylindricalarrangement. The first face 1004 can be provided having the relativelylarge openings 1005 and the second face 1006 can be provided having therelatively small openings. When the filtration media pack 1000 isfanned, enhanced spacing is provided between the pleats at the secondface 1006. As a result, the arrangement shown in FIGS. 30 and 31 can beadvantageous when dirty air flows into the filtration media pack via thesecond flow face 1006 and exits the filtration media pack via the firstflow face 1004.

By fanning the filtration media pack, enhanced separation between themedia surfaces and enhanced media area (as a result of a lack ofmasking) can be provided for receiving the dirty air, and a relativelylarge volume can be provided as the downstream or clean side volume sothat the fluid can flow out of the filtration media pack with reducedrestriction. As a result of the cylindrical arrangement 1000, therelatively larger volume (calculated as media pack volume) can beprovided on the side open to the inner surface, and the relativelysmaller media pack volume can be provided on the side open to the outersurface

In other arrangements, the pleated media is configured or arrangedaround an open central area. An example of such a filter arrangement isdepicted in FIGS. 32 and 33. Referring to FIG. 32, a filter arrangement1030 is depicted. The filter arrangement 1030 comprises first and secondend caps 1032 and 1034 having pleated media 1036 extending therebetween. The pleats of the pleated media 1036 generally extend in adirection between the end caps 1032 and 1034. The particular filterarrangement 1030 of FIG. 32 has an outer liner 1040, shown broken awayat one location, for viewing pleats. (Although pleats can typically beviewed through the liner 1040, the arrangement 1030 shown in FIG. 32 isdrawn w/o showing the pleats through the liner so as to avoid obscuringother features of the arrangement.) The outer liner 1040 shown comprisesexpanded metal, although a variety of alternative outer liners,including plastic and paper ones, can be used. In some instances, anouter liner is simply not used. Attention is also directed to FIG. 33,which is a side perspective view of arrangement 1030, showing end caps1032 and 1034. Pleat folds 1036 are shown, as is outer liner 1040. Forthe particular arrangement 1030 of FIG. 33, a direction perpendicular tothe pleat direction is generally a circumference of the filterarrangement 1030, indicated by the double headed arrow 1042.

The particular filter arrangement 1030 depicted is generallycylindrical, although alternatives are possible. Typically, suchelements as element 1030 have an open end cap, in this instancecorresponding to end cap 1032, and a closed end cap, in this instancecorresponding to end cap 1034, although alternatives are possible. Theterm “open” when used in reference to an end cap, is meant to refer toan end cap which has an open central aperture 1044 to allow air flowbetween an interior space 1046 of the filter arrangement 1030 and theexterior, without passage through the media 1036. A closed end cap, bycomparison, is an end cap which has no aperture therein. Although notdepicted, flutes will typically be arranged in a direction from outerpleat folds of the pleated media 1036 perpendicularly (or nearperpendicularly) into the interior of the element toward the innervolume 1046. However, it will be understood that the flutes do not haveto run perpendicular to the outer pleat folds.

A variety of arrangements have been developed for end caps 1032 and1034. The end caps may comprise polymeric material molded to the media.Alternatively they may comprise metal end caps or other preformed endcaps secured to the media, with an appropriate adhesive or pottingagent. The particular depicted end caps 1032 and 1034 are molded endcaps, each comprising compressible foamed polyurethane. End cap 1032 isshown with a housing seal 1050, for sealing the element 1030 in ahousing during use. The depicted seal 1050 is an inside radial seal,although outside radial seals and axial seals are also possible.

It is noted that the element may include an inner liner 1052 extendingbetween end caps 1032 and 1034 along an inside of the media 1030 asshown in FIG. 33, although in some arrangements such liners areoptional. The inside liner, if used, can be metal, such as expandedmetal or perforated metal, or it can be plastic or paper (for example).

An arrangement such as that depicted in FIGS. 32 and 33 are sometimesreferenced herein as a “cylindrical arrangement,” using “cylindricallyconfigured” media, or by similar characterizations. Not all filterarrangements that utilize a tubular media are configured as cylinders.An example of this is illustrated in FIG. 34. Referring to FIG. 34, afilter arrangement 1100 comprises extension of media 1102 which ispleated, with pleat direction extending in the directions of arrow 1004.Filter arrangement 1100 is somewhat conical having a wide end 1106 and anarrow end 1108. At wide end 1106 is positioned an end cap 1107, and atnarrow end 1108 is positioned an end cap 1109. As with the cylindricalarrangement, a variety of open and closed end caps can be used. For thespecific example depicted, end cap 1107 is open and end cap 1108 isclosed.

Filter arrangement 1100 includes outer support screen 1010 extendingbetween end cap 1107 and 1009. The particular arrangement 1100 includesno inner support screen although one could be used. The filter element1100 includes a seal arrangement 1112, in this instance an axial seal,although an inside or outside radial seal is possible. Element 1100includes a non-continuously threaded mounting arrangement, 1114, formounting a housing. The arrangement 1100 is generally described indetail in PCT/US2003/33952 filed Oct. 23, 2003, incorporated herein byreference.

Alternative configurations for media pleat packs and filter elements arepossible, such as those taught in published U.S. Patent Application No.20070209343 entitled “Filter Assembly with Pleated Media Pockets andMethods (Ser. No. 11/683,287), assigned to Donaldson Company Inc., andincorporated herein by reference in its entirety.

The filter elements can be utilized in various housing arrangements, andthe filter elements can be replaced or cleaned or refurbishedperiodically, as desired. Cleaning can comprise, for example, mechanicalcleaning, pulse cleaning, or reverse fluid flow cleaning. In the case ofair filtration, the housing can be provided as part of an air cleanerfor various air cleaning or processing applications including engine airintake, turbine intake, dust collection, and heating and airconditioning. In the case of liquid filtration, the housing can be partof a liquid cleaner for cleaning or processing, for example, water, oil,fuel, and hydraulic fluid.

The above specification provides a complete description of the presentinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

I claim:
 1. A pleated filtration media pack comprising: (a) filtrationmedia having a first set of pleat folds forming a first face of themedia pack and a second set of pleat folds forming a second face of themedia pack, such that the filtration media extends between the first setof pleat folds and the second set of pleat folds in a back and fortharrangement; and (b) a plurality of flutes formed in the filtrationmedia, said flutes having a length extending between the first andsecond faces of the media pack; wherein at least a portion of theplurality of flutes demonstrate a taper from the first face of the mediapack to the second face of the media pack; and wherein the portion ofthe plurality of flutes demonstrating a taper have a taper in crosssectional area and a substantially uniform height from the first face ofthe media pack to the second face of the media pack; and wherein eachflute has a flute width D1 and a media length along each flute width D2,wherein D1 and D2 remain constant along the length of the flute; whereinat least 25% of the flutes in the pleated filtration media pack compriseat least one ridge between adjacent flute peaks and extending along atleast 25% of the flute length between the first set of pleat folds andthe second set of pleat folds, where each ridge is a line ofintersection between differently-sloped media portions; and wherein theflute profiles define the first set of pleat folds and the second set ofpleat folds.
 2. The pleated filtration media pack of claim 1, whereinthe portion of the plurality of flutes demonstrating a taper have asubstantially uniform taper from the first face to the second face ofthe media pack.
 3. The pleated filtration media pack of claim 1, whereinthe portion of the plurality of flutes demonstrating a taper have ataper in cross sectional area and a substantially uniform width from thefirst face of the media pack to the second face of the media pack. 4.The pleated filtration media pack of claim 1, wherein the filtrationmedia comprises greater than 90 percent cellulose fibers by weight ofthe fibers in the filtration media.
 5. The pleated filtration media packof claim 1, wherein the filtration media has a dry stretch rupturethreshold of less than 10 percent.
 6. A pleated filtration media packaccording to claim 1, wherein the filtration media exhibits a mediavolume asymmetry of at least 10%.
 7. A pleated filtration media packaccording to claim 1, wherein the flutes exhibit a width to heightaspect ratio range of 4 to
 8. 8. A pleated filtration media packaccording to claim 1, wherein the flutes have a media cord percentage ofat least 1%.
 9. A pleated filtration media pack according to claim 1,wherein the flutes exhibit a D2/D1 value of at least 1.1.
 10. A pleatedfiltration media pack according to claim 1, wherein at least 25% of theflutes in the pleated filtration media pack comprise at least two ridgesbetween adjacent flute peaks.
 11. A pleated filtration media packaccording to claim 10, wherein the ridges are non-parallel to oneanother.
 12. A pleated filtration media pack comprising: (a) filtrationmedia having a first set of pleat folds forming a first face of themedia pack and a second set of pleat folds forming a second face of themedia pack, such that the filtration media extends between the first setof pleat folds and the second set of pleat folds in a back and fortharrangement to define pleats defining a length extending from the firstface to the second face and a width perpendicular to the length; and (b)a plurality of flutes formed in the filtration media, said flutesextending between the first and second faces of the media pack; whereinat least a portion of the plurality of flutes demonstrate a taper fromthe first face of the media pack to the second face of the media packand wherein the length of the media defining each of the first set ofpleat folds, each of the second set of pleat folds, and the width ofeach of the pleats from the first face to the second face of the mediapack are equal.
 13. The pleated filtration media pack of claim 12,wherein the filtration media comprises at least 90 percent cellulosefibers by weight of the fibers in the filtration media.
 14. The pleatedfiltration media pack of claim 12, wherein the filtration media has adry stretch rupture threshold of less than 10 percent.
 15. A pleatedfiltration media pack according to claim 12, wherein the filtrationmedia exhibits a media volume asymmetry of at least 10%.
 16. A pleatedfiltration media pack according to claim 12, at least one of theplurality of flutes comprises a peak with a tip formed therein such thatthe tip extends beyond the general profile of the flute.
 17. A pleatedfiltration media pack according to claim 12 wherein at least 25% of theflutes in the pleated filtration media pack comprise at least two ridgesbetween adjacent flute peaks, wherein each ridge is a discontinuity inthe curvature of the flute.
 18. A pleated filtration media packcomprising: (a) filtration media having a first set of pleat foldsforming a first face of the media pack and a second set of pleat foldsforming a second face of the media pack, such that the filtration mediaextends between the first set of pleat folds and the second set of pleatfolds in a back and forth arrangement; and (b) a plurality of flutesformed in the filtration media, said flutes extending between the firstand second faces of the media pack; wherein at least a portion of theplurality of flutes demonstrate a taper from the first face of the mediapack to the second face of the media pack, wherein less than 10 percentof the media in the media pack is masked by other media in the mediapack, and wherein each flute has a flute width D1 and a media lengthalong each flute width D2, wherein D1 and D2 remain constant along thelength of the flute, and wherein the flute profiles define the first setof pleat folds and the second set of pleat folds.
 19. The pleatedfiltration media pack of claim 18, wherein the filtration media has adry stretch rupture threshold of less than 10 percent.
 20. A pleatedfiltration media pack according to claim 18, wherein the filtrationmedia exhibits a media volume asymmetry of at least 10%.
 21. A pleatedfiltration media pack according to claim 18, wherein the filtrationmedia exhibits a media volume asymmetry of at least 50%.
 22. A pleatedfiltration media pack according to claim 18 wherein at least 25% of theflutes in the pleated filtration media pack comprise at least two ridgesbetween adjacent flute peaks, wherein each ridge is a discontinuity inthe curvature of the flute.
 23. A pleated filtration media packaccording to claim 22, wherein the ridges are non-parallel to oneanother.
 24. The pleated filtration media pack of claim 1, wherein thefiltration media has at least one cross section wherein the flutes havea media cross-sectional area asymmetry greater than 50%.
 25. A pleatedfiltration media pack according to claim 12, wherein the flutes exhibita width to height aspect ratio range of 4 to
 8. 26. A pleated filtrationmedia pack according to claim 18, wherein the flutes extend at an angleof about 60 degrees to about 110 degrees relative to one of the firstface or the second face.